automated translation to f-strings using flynt with --aggressive and patched to not pointlessly call int()

src/calibre/build_forms.py

@@ -87,7 +87,7 @@ def build_forms(srcdir, info=None, summary=False, check_for_migration=False, che
             open(compiled_form, 'wb').write(dat)
             num += 1
     if num:
-        info('Compiled %d forms' % num)
+        info(f'Compiled {num} forms')
     if check_icons:
         resource_dir = os.path.join(os.path.dirname(srcdir), 'resources')
         ensure_icons_built(resource_dir, force_compile, info)

src/calibre/customize/ui.py

@@ -808,7 +808,7 @@ def initialize_plugins(perf=False):
     sys.stdout, sys.stderr = ostdout, ostderr
     if perf:
         for x in sorted(times, key=lambda x: times[x]):
-            print('%50s: %.3f'%(x, times[x]))
+            print(f'{x:50}: {times[x]:.3f}')
     _initialized_plugins.sort(key=lambda x: x.priority, reverse=True)
     reread_filetype_plugins()
     reread_metadata_plugins()

src/calibre/customize/zipplugin.py

@@ -350,7 +350,7 @@ class CalibrePluginFinder:
             c = 0
             while True:
                 c += 1
-                plugin_name = 'dummy%d'%c
+                plugin_name = f'dummy{c}'
                 if plugin_name not in self.loaded_plugins:
                     break
         else:

src/calibre/db/__init__.py

@@ -93,7 +93,7 @@ def get_data_as_dict(self, prefix=None, authors_as_string=False, ids=None, conve
         'languages'}.union(set(fdata))
     for x, data in iteritems(fdata):
         if data['datatype'] == 'series':
-            FIELDS.add('%d_index'%x)
+            FIELDS.add(f'{x}_index')
     data = []
     for record in self.data:
         if record is None:

src/calibre/db/backend.py

@@ -614,11 +614,11 @@ class DB:
             from calibre.library.coloring import migrate_old_rule
             old_rules = []
             for i in range(1, 6):
-                col = self.prefs.get('column_color_name_%d' % i, None)
+                col = self.prefs.get(f'column_color_name_{i}', None)
-                templ = self.prefs.get('column_color_template_%d' % i, None)
+                templ = self.prefs.get(f'column_color_template_{i}', None)
                 if col and templ:
                     try:
-                        del self.prefs['column_color_name_%d' % i]
+                        del self.prefs[f'column_color_name_{i}']
                         rules = migrate_old_rule(self.field_metadata, templ)
                         for templ in rules:
                             old_rules.append((col, templ))
@@ -1410,7 +1410,7 @@ class DB:
                 with closing(Connection(tmpdb)) as conn:
                     shell = Shell(db=conn, encoding='utf-8')
                     shell.process_command('.read ' + fname.replace(os.sep, '/'))
-                    conn.execute('PRAGMA user_version=%d;'%uv)
+                    conn.execute(f'PRAGMA user_version={uv};')
 
                 self.close(unload_formatter_functions=False)
                 try:
@@ -1495,7 +1495,7 @@ class DB:
         # windows).
         l = (self.PATH_LIMIT - (extlen // 2) - 2) if iswindows else ((self.PATH_LIMIT - extlen - 2) // 2)
         if l < 5:
-            raise ValueError('Extension length too long: %d' % extlen)
+            raise ValueError(f'Extension length too long: {extlen}')
         author = ascii_filename(author)[:l]
         title  = ascii_filename(title.lstrip())[:l].rstrip()
         if not title:
@@ -1510,7 +1510,7 @@ class DB:
     # Database layer API {{{
 
     def custom_table_names(self, num):
-        return 'custom_column_%d'%num, 'books_custom_column_%d_link'%num
+        return f'custom_column_{num}', f'books_custom_column_{num}_link'
 
     @property
     def custom_tables(self):
@@ -1628,7 +1628,7 @@ class DB:
     def format_hash(self, book_id, fmt, fname, path):
         path = self.format_abspath(book_id, fmt, fname, path)
         if path is None:
-            raise NoSuchFormat('Record %d has no fmt: %s'%(book_id, fmt))
+            raise NoSuchFormat(f'Record {book_id} has no fmt: {fmt}')
         sha = hashlib.sha256()
         with open(path, 'rb') as f:
             while True:

src/calibre/db/cache.py

@@ -992,7 +992,7 @@ class Cache:
             name = self.fields['formats'].format_fname(book_id, fmt)
             path = self._field_for('path', book_id).replace('/', os.sep)
         except:
-            raise NoSuchFormat('Record %d has no fmt: %s'%(book_id, fmt))
+            raise NoSuchFormat(f'Record {book_id} has no fmt: {fmt}')
         return self.backend.format_hash(book_id, fmt, name, path)
 
     @api
@@ -1222,7 +1222,7 @@ class Cache:
             name = self.fields['formats'].format_fname(book_id, fmt)
             path = self._field_for('path', book_id).replace('/', os.sep)
         except (KeyError, AttributeError):
-            raise NoSuchFormat('Record %d has no %s file'%(book_id, fmt))
+            raise NoSuchFormat(f'Record {book_id} has no {fmt} file')
 
         return self.backend.copy_format_to(book_id, fmt, name, path, dest,
                                                use_hardlink=use_hardlink, report_file_size=report_file_size)
@@ -2374,7 +2374,7 @@ class Cache:
         removed. '''
         missing = frozenset(val_map) - self._all_book_ids()
         if missing:
-            raise ValueError('add_custom_book_data: no such book_ids: %d'%missing)
+            raise ValueError(f'add_custom_book_data: no such book_ids: {missing}')
         self.backend.add_custom_data(name, val_map, delete_first)
 
     @read_api

src/calibre/db/cli/cmd_custom_columns.py

@@ -43,5 +43,5 @@ def main(opts, args, dbctx):
             prints(pformat(data))
             print('\n')
         else:
-            prints(col, '(%d)'%data['num'])
+            prints(col, f"({data['num']})")
     return 0

src/calibre/db/legacy.py

@@ -654,7 +654,7 @@ class LibraryDatabase:
         book_id = index if index_is_id else self.id(index)
         ans = self.new_api.format_abspath(book_id, fmt)
         if ans is None:
-            raise NoSuchFormat('Record %d has no format: %s'%(book_id, fmt))
+            raise NoSuchFormat(f'Record {book_id} has no format: {fmt}')
         return ans
 
     def format_files(self, index, index_is_id=False):

src/calibre/db/schema_upgrades.py

@@ -23,13 +23,13 @@ class SchemaUpgrade:
         try:
             while True:
                 uv = next(self.db.execute('pragma user_version'))[0]
-                meth = getattr(self, 'upgrade_version_%d'%uv, None)
+                meth = getattr(self, f'upgrade_version_{uv}', None)
                 if meth is None:
                     break
                 else:
-                    prints('Upgrading database to version %d...'%(uv+1))
+                    prints(f'Upgrading database to version {uv + 1}...')
                     meth()
-                    self.db.execute('pragma user_version=%d'%(uv+1))
+                    self.db.execute(f'pragma user_version={uv + 1}')
         except:
             self.db.execute('ROLLBACK')
             raise

src/calibre/db/tests/filesystem.py

@@ -279,7 +279,7 @@ class FilesystemTest(BaseTest):
                 self.assertFalse(importer.corrupted_files)
                 self.assertEqual(cache.all_book_ids(), ic.all_book_ids())
                 for book_id in cache.all_book_ids():
-                    self.assertEqual(cache.cover(book_id), ic.cover(book_id), 'Covers not identical for book: %d' % book_id)
+                    self.assertEqual(cache.cover(book_id), ic.cover(book_id), f'Covers not identical for book: {book_id}')
                     for fmt in cache.formats(book_id):
                         self.assertEqual(cache.format(book_id, fmt), ic.format(book_id, fmt))
                         self.assertEqual(cache.format_metadata(book_id, fmt)['mtime'], cache.format_metadata(book_id, fmt)['mtime'])

src/calibre/db/tests/legacy.py

@@ -544,7 +544,7 @@ class LegacyTest(BaseTest):
         n = now()
         ndb = self.init_legacy(self.cloned_library)
         amap = ndb.new_api.get_id_map('authors')
-        sorts = [(aid, 's%d' % aid) for aid in amap]
+        sorts = [(aid, f's{aid}') for aid in amap]
         db = self.init_old(self.cloned_library)
         run_funcs(self, db, ndb, (
             ('+format_metadata', 1, 'FMT1', itemgetter('size')),

src/calibre/db/tests/reading.py

@@ -126,8 +126,7 @@ class ReadingTest(BaseTest):
                 if isinstance(val, tuple) and 'authors' not in field and 'languages' not in field:
                     val, expected_val = set(val), set(expected_val)
                 self.assertEqual(expected_val, val,
-                        'Book id: %d Field: %s failed: %r != %r'%(
+                        f'Book id: {book_id} Field: {field} failed: {expected_val!r} != {val!r}')
-                            book_id, field, expected_val, val))
         # }}}
 
     def test_sorting(self):  # {{{
@@ -206,7 +205,7 @@ class ReadingTest(BaseTest):
             ('title', True)]), 'Subsort failed')
         from calibre.ebooks.metadata.book.base import Metadata
         for i in range(7):
-            cache.create_book_entry(Metadata('title%d' % i), apply_import_tags=False)
+            cache.create_book_entry(Metadata(f'title{i}'), apply_import_tags=False)
         cache.create_custom_column('one', 'CC1', 'int', False)
         cache.create_custom_column('two', 'CC2', 'int', False)
         cache.create_custom_column('three', 'CC3', 'int', False)

src/calibre/db/tests/utils.py

@@ -27,7 +27,7 @@ class UtilsTest(BaseTest):
         total = 0
         for i in range(1, num+1):
             sz = i * 1000
-            c.insert(i, i, (('%d'%i) * sz).encode('ascii'))
+            c.insert(i, i, (f'{i}' * sz).encode('ascii'))
             total += sz
         return total
 
@@ -44,7 +44,7 @@ class UtilsTest(BaseTest):
         for i in (3, 4, 2, 5, 1):
             data, ts = c[i]
             self.assertEqual(i, ts, 'timestamp not correct')
-            self.assertEqual((('%d'%i) * (i*1000)).encode('ascii'), data)
+            self.assertEqual((f'{i}' * (i*1000)).encode('ascii'), data)
         c.set_group_id('a')
         self.basic_fill(c)
         order = tuple(c.items)

src/calibre/db/tests/writing.py

@@ -387,7 +387,7 @@ class WritingTest(BaseTest):
         for book_id in book_ids:
             raw = cache.read_backup(book_id)
             opf = OPF(BytesIO(raw))
-            ae(opf.title, 'title%d'%book_id)
+            ae(opf.title, f'title{book_id}')
             ae(opf.authors, ['author1', 'author2'])
         tested_fields = 'title authors tags'.split()
         before = {f:cache.all_field_for(f, book_ids) for f in tested_fields}
@@ -439,9 +439,9 @@ class WritingTest(BaseTest):
         ae(cache.set_cover({bid:img for bid in (1, 2, 3)}), {1, 2, 3})
         old = self.init_old()
         for book_id in (1, 2, 3):
-            ae(cache.cover(book_id), img, 'Cover was not set correctly for book %d' % book_id)
+            ae(cache.cover(book_id), img, f'Cover was not set correctly for book {book_id}')
             ae(cache.field_for('cover', book_id), 1)
-            ae(old.cover(book_id, index_is_id=True), img, 'Cover was not set correctly for book %d' % book_id)
+            ae(old.cover(book_id, index_is_id=True), img, f'Cover was not set correctly for book {book_id}')
             self.assertTrue(old.has_cover(book_id))
         old.close()
         old.break_cycles()
@@ -771,9 +771,9 @@ class WritingTest(BaseTest):
         conn.execute('INSERT INTO publishers (name) VALUES ("MŪS")')
         uid = conn.last_insert_rowid()
         conn.execute('DELETE FROM books_publishers_link')
-        conn.execute('INSERT INTO books_publishers_link (book,publisher) VALUES (1, %d)' % lid)
+        conn.execute(f'INSERT INTO books_publishers_link (book,publisher) VALUES (1, {lid})')
-        conn.execute('INSERT INTO books_publishers_link (book,publisher) VALUES (2, %d)' % uid)
+        conn.execute(f'INSERT INTO books_publishers_link (book,publisher) VALUES (2, {uid})')
-        conn.execute('INSERT INTO books_publishers_link (book,publisher) VALUES (3, %d)' % uid)
+        conn.execute(f'INSERT INTO books_publishers_link (book,publisher) VALUES (3, {uid})')
         cache.reload_from_db()
         t = cache.fields['publisher'].table
         for x in (lid, uid):

src/calibre/db/utils.py

@@ -295,9 +295,7 @@ class ThumbnailCache:
                 self._load_index()
             self._invalidate_sizes()
             ts = (f'{timestamp:.2f}').replace('.00', '')
-            path = '%s%s%s%s%d-%s-%d-%dx%d' % (
+            path = f'{self.group_id}{os.sep}{book_id % 100}{os.sep}{book_id}-{ts}-{len(data)}-{self.thumbnail_size[0]}x{self.thumbnail_size[1]}'
-                self.group_id, os.sep, book_id % 100, os.sep,
-                book_id, ts, len(data), self.thumbnail_size[0], self.thumbnail_size[1])
             path = os.path.join(self.location, path)
             key = (self.group_id, book_id)
             e = self.items.pop(key, None)
@@ -371,7 +369,7 @@ class ThumbnailCache:
                     self._remove((self.group_id, book_id))
             elif os.path.exists(self.location):
                 try:
-                    raw = '\n'.join('%s %d' % (self.group_id, book_id) for book_id in book_ids)
+                    raw = '\n'.join(f'{self.group_id} {book_id}' for book_id in book_ids)
                     with open(os.path.join(self.location, 'invalidate'), 'ab') as f:
                         f.write(raw.encode('ascii'))
                 except OSError as err:

src/calibre/devices/kindle/bookmark.py

@@ -153,7 +153,7 @@ class Bookmark:  # {{{
                         marker_found = 0
                         text = ''
                         search_str1 = f'{mi.title}'
-                        search_str2 = '- Highlight Loc. %d' % (displayed_location)
+                        search_str2 = f'- Highlight Loc. {displayed_location}'
                         for line in f2:
                             if marker_found == 0:
                                 if line.startswith(search_str1):

src/calibre/devices/kobo/driver.py

@@ -830,7 +830,7 @@ class KOBO(USBMS):
             cursor.close()
 
     def set_readstatus(self, connection, ContentID, ReadStatus):
-        debug_print('Kobo::set_readstatus - ContentID=%s, ReadStatus=%d' % (ContentID, ReadStatus))
+        debug_print(f'Kobo::set_readstatus - ContentID={ContentID}, ReadStatus={ReadStatus}')
         cursor = connection.cursor()
         t = (ContentID,)
         cursor.execute('select DateLastRead, ReadStatus  from Content where BookID is Null and ContentID = ?', t)
@@ -851,7 +851,7 @@ class KOBO(USBMS):
             t = (ReadStatus, datelastread, ContentID,)
 
             try:
-                debug_print('Kobo::set_readstatus - Making change - ContentID=%s, ReadStatus=%d, DateLastRead=%s' % (ContentID, ReadStatus, datelastread))
+                debug_print(f'Kobo::set_readstatus - Making change - ContentID={ContentID}, ReadStatus={ReadStatus}, DateLastRead={datelastread}')
                 cursor.execute("update content set ReadStatus=?,FirstTimeReading='false',DateLastRead=? where BookID is Null and ContentID = ?", t)
             except:
                 debug_print('    Database Exception: Unable to update ReadStatus')
@@ -1742,8 +1742,7 @@ class KOBOTOUCH(KOBO):
             if show_debug:
                 debug_print(f"KoboTouch:update_booklist - title='{title}'", f'ContentType={ContentType}', 'isdownloaded=', isdownloaded)
                 debug_print(
-                    '         prefix=%s, DateCreated=%s, readstatus=%d, MimeType=%s, expired=%d, favouritesindex=%d, accessibility=%d, isdownloaded=%s'%
+                    f'         prefix={prefix}, DateCreated={DateCreated}, readstatus={readstatus}, MimeType={MimeType}, expired={expired}, favouritesindex={favouritesindex}, accessibility={accessibility}, isdownloaded={isdownloaded}')
-                (prefix, DateCreated, readstatus, MimeType, expired, favouritesindex, accessibility, isdownloaded,))
             changed = False
             try:
                 lpath = path.partition(self.normalize_path(prefix))[2]
@@ -1845,7 +1844,7 @@ class KOBOTOUCH(KOBO):
                 if idx is not None:  # and not (accessibility == 1 and isdownloaded == 'false'):
                     if show_debug:
                         self.debug_index = idx
-                        debug_print('KoboTouch:update_booklist - idx=%d'%idx)
+                        debug_print(f'KoboTouch:update_booklist - idx={idx}')
                         debug_print(f'KoboTouch:update_booklist - lpath={lpath}')
                         debug_print('KoboTouch:update_booklist - bl[idx].device_collections=', bl[idx].device_collections)
                         debug_print('KoboTouch:update_booklist - playlist_map=', playlist_map)
@@ -2090,7 +2089,7 @@ class KOBOTOUCH(KOBO):
                 # self.report_progress((i) / float(books_on_device), _('Getting list of books on device...'))
                 show_debug = self.is_debugging_title(row['Title'])
                 if show_debug:
-                    debug_print('KoboTouch:books - looping on database - row=%d' % i)
+                    debug_print(f'KoboTouch:books - looping on database - row={i}')
                     debug_print("KoboTouch:books - title='{}'".format(row['Title']), 'authors=', row['Attribution'])
                     debug_print('KoboTouch:books - row=', row)
                 if not hasattr(row['ContentID'], 'startswith') or row['ContentID'].lower().startswith(
@@ -2506,7 +2505,7 @@ class KOBOTOUCH(KOBO):
             if self._card_a_prefix is not None:
                 ContentID = ContentID.replace(self._card_a_prefix, 'file:///mnt/sd/')
         else:  # ContentType = 16
-            debug_print("KoboTouch:contentid_from_path ContentType other than 6 - ContentType='%d'"%ContentType, f"path='{path}'")
+            debug_print(f"KoboTouch:contentid_from_path ContentType other than 6 - ContentType='{ContentType}'", f"path='{path}'")
             ContentID = path
             ContentID = ContentID.replace(self._main_prefix, 'file:///mnt/onboard/')
             if self._card_a_prefix is not None:
@@ -2720,9 +2719,8 @@ class KOBOTOUCH(KOBO):
                 if not prefs['manage_device_metadata'] == 'manual' and delete_empty_collections:
                     debug_print('KoboTouch:update_device_database_collections - about to clear empty bookshelves')
                     self.delete_empty_bookshelves(connection)
-                debug_print('KoboTouch:update_device_database_collections - Number of series set=%d Number of books=%d' % (self.series_set, books_in_library))
+                debug_print(f'KoboTouch:update_device_database_collections - Number of series set={self.series_set} Number of books={books_in_library}')
-                debug_print('KoboTouch:update_device_database_collections - Number of core metadata set=%d Number of books=%d' % (
+                debug_print(f'KoboTouch:update_device_database_collections - Number of core metadata set={self.core_metadata_set} Number of books={books_in_library}')
-                    self.core_metadata_set, books_in_library))
 
                 self.dump_bookshelves(connection)
 
@@ -2916,8 +2914,7 @@ class KOBOTOUCH(KOBO):
                 for ending, cover_options in self.cover_file_endings().items():
                     kobo_size, min_dbversion, max_dbversion, is_full_size = cover_options
                     if show_debug:
-                        debug_print('KoboTouch:_upload_cover - library_cover_size=%s -> kobo_size=%s, min_dbversion=%d max_dbversion=%d, is_full_size=%s' % (
+                        debug_print(f'KoboTouch:_upload_cover - library_cover_size={library_cover_size} -> kobo_size={kobo_size}, min_dbversion={min_dbversion} max_dbversion={max_dbversion}, is_full_size={is_full_size}')
-                            library_cover_size, kobo_size, min_dbversion, max_dbversion, is_full_size))
 
                     if self.dbversion >= min_dbversion and self.dbversion <= max_dbversion:
                         if show_debug:
@@ -4229,7 +4226,7 @@ class KOBOTOUCH(KOBO):
         if i == 0:
             prints('No shelves found!!')
         else:
-            prints('Number of shelves=%d'%i)
+            prints(f'Number of shelves={i}')
 
         prints('\nBooks on shelves on device:')
         cursor.execute(shelfcontent_query)
@@ -4241,7 +4238,7 @@ class KOBOTOUCH(KOBO):
         if i == 0:
             prints('No books are on any shelves!!')
         else:
-            prints('Number of shelved books=%d'%i)
+            prints(f'Number of shelved books={i}')
 
         cursor.close()
         debug_print('KoboTouch:dump_bookshelves - end')

src/calibre/devices/mtp/unix/driver.py

@@ -218,7 +218,7 @@ class MTP_DEVICE(MTPDeviceBase):
         self.dev = self._filesystem_cache = None
 
     def format_errorstack(self, errs):
-        return '\n'.join('%d:%s'%(code, as_unicode(msg)) for code, msg in errs)
+        return '\n'.join(f'{code}:{as_unicode(msg)}' for code, msg in errs)
 
     @synchronous
     def open(self, connected_device, library_uuid):

src/calibre/devices/paladin/driver.py

@@ -122,7 +122,7 @@ class PALADIN(USBMS):
 
                 try:
                     device_offset = max(time_offsets, key=lambda a: time_offsets.get(a))
-                    debug_print('Device Offset: %d ms'%device_offset)
+                    debug_print(f'Device Offset: {device_offset} ms')
                     self.device_offset = device_offset
                 except ValueError:
                     debug_print('No Books To Detect Device Offset.')
@@ -249,7 +249,7 @@ class PALADIN(USBMS):
         sequence_max = sequence_min
         sequence_dirty = 0
 
-        debug_print('Book Sequence Min: %d, Source Id: %d'%(sequence_min,source_id))
+        debug_print(f'Book Sequence Min: {sequence_min}, Source Id: {source_id}')
 
         try:
             cursor = connection.cursor()
@@ -283,7 +283,7 @@ class PALADIN(USBMS):
 
         # If the database is 'dirty', then we should fix up the Ids and the sequence number
         if sequence_dirty == 1:
-            debug_print('Book Sequence Dirty for Source Id: %d'%source_id)
+            debug_print(f'Book Sequence Dirty for Source Id: {source_id}')
             sequence_max = sequence_max + 1
             for book, bookId in db_books.items():
                 if bookId < sequence_min:
@@ -302,7 +302,7 @@ class PALADIN(USBMS):
                     cursor.execute(query, t)
 
             self.set_database_sequence_id(connection, 'books', sequence_max)
-            debug_print('Book Sequence Max: %d, Source Id: %d'%(sequence_max,source_id))
+            debug_print(f'Book Sequence Max: {sequence_max}, Source Id: {source_id}')
 
         cursor.close()
         return db_books
@@ -355,7 +355,7 @@ class PALADIN(USBMS):
                         book.mime or mime_type_ext(path_to_ext(lpath)))
                 cursor.execute(query, t)
                 book.bookId = connection.last_insert_rowid()
-                debug_print('Inserted New Book: (%u) '%book.bookId + book.title)
+                debug_print(f'Inserted New Book: ({book.bookId}) ' + book.title)
             else:
                 query = '''
                 UPDATE books
@@ -386,7 +386,7 @@ class PALADIN(USBMS):
         sequence_max = sequence_min
         sequence_dirty = 0
 
-        debug_print('Collection Sequence Min: %d, Source Id: %d'%(sequence_min,source_id))
+        debug_print(f'Collection Sequence Min: {sequence_min}, Source Id: {source_id}')
 
         try:
             cursor = connection.cursor()
@@ -415,7 +415,7 @@ class PALADIN(USBMS):
 
         # If the database is 'dirty', then we should fix up the Ids and the sequence number
         if sequence_dirty == 1:
-            debug_print('Collection Sequence Dirty for Source Id: %d'%source_id)
+            debug_print(f'Collection Sequence Dirty for Source Id: {source_id}')
             sequence_max = sequence_max + 1
             for collection, collectionId in db_collections.items():
                 if collectionId < sequence_min:
@@ -434,13 +434,13 @@ class PALADIN(USBMS):
                     cursor.execute(query, t)
 
             self.set_database_sequence_id(connection, 'tags', sequence_max)
-            debug_print('Collection Sequence Max: %d, Source Id: %d'%(sequence_max,source_id))
+            debug_print(f'Collection Sequence Max: {sequence_max}, Source Id: {source_id}')
 
         # Fix up the collections table now...
         sequence_dirty = 0
         sequence_max = sequence_min
 
-        debug_print('Collections Sequence Min: %d, Source Id: %d'%(sequence_min,source_id))
+        debug_print(f'Collections Sequence Min: {sequence_min}, Source Id: {source_id}')
 
         query = 'SELECT _id FROM booktags'
         cursor.execute(query)
@@ -454,7 +454,7 @@ class PALADIN(USBMS):
                 sequence_max = max(sequence_max, row[0])
 
         if sequence_dirty == 1:
-            debug_print('Collections Sequence Dirty for Source Id: %d'%source_id)
+            debug_print(f'Collections Sequence Dirty for Source Id: {source_id}')
             sequence_max = sequence_max + 1
             for pairId in db_collection_pairs:
                 if pairId < sequence_min:
@@ -465,7 +465,7 @@ class PALADIN(USBMS):
                     sequence_max = sequence_max + 1
 
             self.set_database_sequence_id(connection, 'booktags', sequence_max)
-            debug_print('Collections Sequence Max: %d, Source Id: %d'%(sequence_max,source_id))
+            debug_print(f'Collections Sequence Max: {sequence_max}, Source Id: {source_id}')
 
         cursor.close()
         return db_collections
@@ -483,7 +483,7 @@ class PALADIN(USBMS):
                     t = (collection,)
                     cursor.execute(query, t)
                     db_collections[collection] = connection.last_insert_rowid()
-                    debug_print('Inserted New Collection: (%u) '%db_collections[collection] + collection)
+                    debug_print(f'Inserted New Collection: ({db_collections[collection]}) ' + collection)
 
                 # Get existing books in collection
                 query = '''

src/calibre/devices/prs505/sony_cache.py

@@ -434,8 +434,7 @@ class XMLCache:
                             book.lpath, book.thumbnail)
                     self.periodicalize_book(book, ext_record)
 
-            debug_print('Timezone votes: %d GMT, %d LTZ, use_tz_var=%s'%
+            debug_print(f'Timezone votes: {gtz_count} GMT, {ltz_count} LTZ, use_tz_var={use_tz_var}')
-                                        (gtz_count, ltz_count, use_tz_var))
             self.update_playlists(i, root, booklist, collections_attributes)
         # Update the device collections because update playlist could have added
         # some new ones.

src/calibre/devices/prst1/driver.py

@@ -210,7 +210,7 @@ class PRST1(USBMS):
 
                 try:
                     device_offset = max(time_offsets, key=lambda a: time_offsets.get(a))
-                    debug_print('Device Offset: %d ms'%device_offset)
+                    debug_print(f'Device Offset: {device_offset} ms')
                     self.device_offset = device_offset
                 except ValueError:
                     debug_print('No Books To Detect Device Offset.')
@@ -362,7 +362,7 @@ class PRST1(USBMS):
         sequence_max = sequence_min
         sequence_dirty = 0
 
-        debug_print('Book Sequence Min: %d, Source Id: %d'%(sequence_min,source_id))
+        debug_print(f'Book Sequence Min: {sequence_min}, Source Id: {source_id}')
 
         try:
             cursor = connection.cursor()
@@ -396,7 +396,7 @@ class PRST1(USBMS):
 
         # If the database is 'dirty', then we should fix up the Ids and the sequence number
         if sequence_dirty == 1:
-            debug_print('Book Sequence Dirty for Source Id: %d'%source_id)
+            debug_print(f'Book Sequence Dirty for Source Id: {source_id}')
             sequence_max = sequence_max + 1
             for book, bookId in db_books.items():
                 if bookId < sequence_min:
@@ -433,7 +433,7 @@ class PRST1(USBMS):
                     cursor.execute(query, t)
 
             self.set_database_sequence_id(connection, 'books', sequence_max)
-            debug_print('Book Sequence Max: %d, Source Id: %d'%(sequence_max,source_id))
+            debug_print(f'Book Sequence Max: {sequence_max}, Source Id: {source_id}')
 
         cursor.close()
         return db_books
@@ -495,7 +495,7 @@ class PRST1(USBMS):
                 book.bookId = self.get_lastrowid(cursor)
                 if upload_covers:
                     self.upload_book_cover(connection, book, source_id)
-                debug_print('Inserted New Book: (%u) '%book.bookId + book.title)
+                debug_print(f'Inserted New Book: ({book.bookId}) ' + book.title)
             else:
                 query = '''
                 UPDATE books
@@ -534,7 +534,7 @@ class PRST1(USBMS):
         sequence_max = sequence_min
         sequence_dirty = 0
 
-        debug_print('Collection Sequence Min: %d, Source Id: %d'%(sequence_min,source_id))
+        debug_print(f'Collection Sequence Min: {sequence_min}, Source Id: {source_id}')
 
         try:
             cursor = connection.cursor()
@@ -563,7 +563,7 @@ class PRST1(USBMS):
 
         # If the database is 'dirty', then we should fix up the Ids and the sequence number
         if sequence_dirty == 1:
-            debug_print('Collection Sequence Dirty for Source Id: %d'%source_id)
+            debug_print(f'Collection Sequence Dirty for Source Id: {source_id}')
             sequence_max = sequence_max + 1
             for collection, collectionId in db_collections.items():
                 if collectionId < sequence_min:
@@ -582,13 +582,13 @@ class PRST1(USBMS):
                     cursor.execute(query, t)
 
             self.set_database_sequence_id(connection, 'collection', sequence_max)
-            debug_print('Collection Sequence Max: %d, Source Id: %d'%(sequence_max,source_id))
+            debug_print(f'Collection Sequence Max: {sequence_max}, Source Id: {source_id}')
 
         # Fix up the collections table now...
         sequence_dirty = 0
         sequence_max = sequence_min
 
-        debug_print('Collections Sequence Min: %d, Source Id: %d'%(sequence_min,source_id))
+        debug_print(f'Collections Sequence Min: {sequence_min}, Source Id: {source_id}')
 
         query = 'SELECT _id FROM collections'
         cursor.execute(query)
@@ -602,7 +602,7 @@ class PRST1(USBMS):
                 sequence_max = max(sequence_max, row[0])
 
         if sequence_dirty == 1:
-            debug_print('Collections Sequence Dirty for Source Id: %d'%source_id)
+            debug_print(f'Collections Sequence Dirty for Source Id: {source_id}')
             sequence_max = sequence_max + 1
             for pairId in db_collection_pairs:
                 if pairId < sequence_min:
@@ -613,7 +613,7 @@ class PRST1(USBMS):
                     sequence_max = sequence_max + 1
 
             self.set_database_sequence_id(connection, 'collections', sequence_max)
-            debug_print('Collections Sequence Max: %d, Source Id: %d'%(sequence_max,source_id))
+            debug_print(f'Collections Sequence Max: {sequence_max}, Source Id: {source_id}')
 
         cursor.close()
         return db_collections
@@ -631,7 +631,7 @@ class PRST1(USBMS):
                     t = (collection, source_id)
                     cursor.execute(query, t)
                     db_collections[collection] = self.get_lastrowid(cursor)
-                    debug_print('Inserted New Collection: (%u) '%db_collections[collection] + collection)
+                    debug_print(f'Inserted New Collection: ({db_collections[collection]}) ' + collection)
 
                 # Get existing books in collection
                 query = '''

src/calibre/devices/scanner.py

@@ -219,8 +219,7 @@ def test_for_mem_leak():
         for i in range(3):
             gc.collect()
         usedmem = memory(startmem)
-        prints('Memory used in %d repetitions of scan(): %.5f KB'%(reps,
+        prints(f'Memory used in {reps} repetitions of scan(): {1024 * usedmem:.5f} KB')
-            1024*usedmem))
         prints('Differences in python object counts:')
         diff_hists(h1, gc_histogram())
         prints()

src/calibre/devices/smart_device_app/driver.py

@@ -853,7 +853,7 @@ class SMART_DEVICE_APP(DeviceConfig, DevicePlugin):
                     json_metadata[key]['book'] = self.json_codec.encode_book_metadata(book['book'])
                     json_metadata[key]['last_used'] = book['last_used']
                     result = as_bytes(json.dumps(json_metadata, indent=2, default=to_json))
-                    fd.write(('%0.7d\n'%(len(result)+1)).encode('ascii'))
+                    fd.write(f'{len(result) + 1:007}\n'.encode('ascii'))
                     fd.write(result)
                     fd.write(b'\n')
                     count += 1
@@ -1943,7 +1943,7 @@ class SMART_DEVICE_APP(DeviceConfig, DevicePlugin):
             try:
                 self.listen_socket.listen(1)
             except:
-                message = 'listen on port %d failed' % port
+                message = f'listen on port {port} failed'
                 self._debug(message)
                 self._close_listen_socket()
                 return message

src/calibre/devices/udisks.py

@@ -28,7 +28,7 @@ def node_mountpoint(node):
 
 
 def basic_mount_options():
-    return ['rw', 'noexec', 'nosuid', 'nodev', 'uid=%d'%os.geteuid(), 'gid=%d'%os.getegid()]
+    return ['rw', 'noexec', 'nosuid', 'nodev', f'uid={os.geteuid()}', f'gid={os.getegid()}']
 
 
 class UDisks:

src/calibre/devices/usbms/device.py

@@ -597,7 +597,7 @@ class Device(DeviceConfig, DevicePlugin):
                 continue
             mp, ret = mount(card, typ)
             if mp is None:
-                print('Unable to mount card (Error code: %d)'%ret, file=sys.stderr)
+                print(f'Unable to mount card (Error code: {ret})', file=sys.stderr)
             else:
                 if not mp.endswith('/'):
                     mp += '/'

src/calibre/devices/winusb.py

@@ -179,10 +179,7 @@ class USB_DEVICE_DESCRIPTOR(Structure):
     )
 
     def __repr__(self):
-        return 'USBDevice(class=0x%x sub_class=0x%x protocol=0x%x vendor_id=0x%x product_id=0x%x bcd=0x%x manufacturer=%d product=%d serial_number=%d)' % (
+        return f'USBDevice(class=0x{self.bDeviceClass:x} sub_class=0x{self.bDeviceSubClass:x} protocol=0x{self.bDeviceProtocol:x} vendor_id=0x{self.idVendor:x} product_id=0x{self.idProduct:x} bcd=0x{self.bcdDevice:x} manufacturer={self.iManufacturer} product={self.iProduct} serial_number={self.iSerialNumber})'
-            self.bDeviceClass, self.bDeviceSubClass, self.bDeviceProtocol,
-            self.idVendor, self.idProduct, self.bcdDevice, self.iManufacturer,
-            self.iProduct, self.iSerialNumber)
 
 
 class USB_ENDPOINT_DESCRIPTOR(Structure):
@@ -935,7 +932,7 @@ def get_usb_info(usbdev, debug=False):  # {{{
                             # randomly after some time of my Kindle being
                             # connected. Disconnecting and reconnecting causes
                             # it to start working again.
-                            prints('Failed to read %s from device, with error: [%d] %s' % (name, err.winerror, as_unicode(err)))
+                            prints(f'Failed to read {name} from device, with error: [{err.winerror}] {as_unicode(err)}')
     finally:
         CloseHandle(handle)
     return ans

src/calibre/ebooks/comic/input.py

@@ -236,7 +236,7 @@ class PageProcessor(list):  # {{{
                     final_fmt = QImage.Format.Format_Indexed8 if uses_256_colors else QImage.Format.Format_Grayscale16
                     if img.format() != final_fmt:
                         img = img.convertToFormat(final_fmt)
-            dest = '%d_%d.%s'%(self.num, i, self.opts.output_format)
+            dest = f'{self.num}_{i}.{self.opts.output_format}'
             dest = os.path.join(self.dest, dest)
             with open(dest, 'wb') as f:
                 f.write(image_to_data(img, fmt=self.opts.output_format))

src/calibre/ebooks/conversion/cli.py

@@ -302,7 +302,7 @@ class ProgressBar:
     def __call__(self, frac, msg=''):
         if msg:
             percent = int(frac*100)
-            self.log('%d%% %s'%(percent, msg))
+            self.log(f'{percent}% {msg}')
 
 
 def create_option_parser(args, log):

src/calibre/ebooks/conversion/plugins/chm_input.py

@@ -131,7 +131,7 @@ class CHMInput(InputFormatPlugin):
         # print('Printing hhcroot')
         # print(etree.tostring(hhcroot, pretty_print=True))
         # print('=============================')
-        log.debug('Found %d section nodes' % toc.count())
+        log.debug(f'Found {toc.count()} section nodes')
         htmlpath = os.path.splitext(hhcpath)[0] + '.html'
         base = os.path.dirname(os.path.abspath(htmlpath))
 

src/calibre/ebooks/conversion/plugins/comic_input.py

@@ -175,7 +175,7 @@ class ComicInput(InputFormatPlugin):
         num_pages_per_comic = []
         for i, x in enumerate(comics_):
             title, fname = x
-            cdir = 'comic_%d'%(i+1) if len(comics_) > 1 else '.'
+            cdir = f'comic_{i + 1}' if len(comics_) > 1 else '.'
             cdir = os.path.abspath(cdir)
             if not os.path.exists(cdir):
                 os.makedirs(cdir)
@@ -228,11 +228,11 @@ class ComicInput(InputFormatPlugin):
                 wrapper_page_href = href(wrappers[0])
                 for i in range(num_pages_per_comic[0]):
                     toc.add_item(f'{wrapper_page_href}#page_{i+1}', None,
-                        _('Page')+' %d'%(i+1), play_order=i)
+                        _('Page')+f' {i + 1}', play_order=i)
 
             else:
                 for i, x in enumerate(wrappers):
-                    toc.add_item(href(x), None, _('Page')+' %d'%(i+1),
+                    toc.add_item(href(x), None, _('Page')+f' {i + 1}',
                             play_order=i)
         else:
             po = 0
@@ -246,12 +246,12 @@ class ComicInput(InputFormatPlugin):
                         wrapper_page_href = href(wrappers[0])
                         for i in range(num_pages):
                             stoc.add_item(f'{wrapper_page_href}#page_{i+1}', None,
-                                    _('Page')+' %d'%(i+1), play_order=po)
+                                    _('Page')+f' {i + 1}', play_order=po)
                             po += 1
                     else:
                         for i, x in enumerate(wrappers):
                             stoc.add_item(href(x), None,
-                                    _('Page')+' %d'%(i+1), play_order=po)
+                                    _('Page')+f' {i + 1}', play_order=po)
                             po += 1
         opf.set_toc(toc)
         with open('metadata.opf', 'wb') as m, open('toc.ncx', 'wb') as n:
@@ -282,7 +282,7 @@ class ComicInput(InputFormatPlugin):
         dir = os.path.dirname(pages[0])
         for i, page in enumerate(pages):
             wrapper = WRAPPER%(XHTML_NS, i+1, os.path.basename(page), i+1)
-            page = os.path.join(dir, 'page_%d.xhtml'%(i+1))
+            page = os.path.join(dir, f'page_{i + 1}.xhtml')
             with open(page, 'wb') as f:
                 f.write(wrapper.encode('utf-8'))
             wrappers.append(page)

src/calibre/ebooks/conversion/plugins/djvu_input.py

@@ -41,7 +41,7 @@ class DJVUInput(InputFormatPlugin):
         c = 0
         while os.path.exists(htmlfile):
             c += 1
-            htmlfile = os.path.join(base, 'index%d.html'%c)
+            htmlfile = os.path.join(base, f'index{c}.html')
         with open(htmlfile, 'wb') as f:
             f.write(html.encode('utf-8'))
         odi = options.debug_pipeline

src/calibre/ebooks/conversion/plugins/fb2_input.py

@@ -110,10 +110,10 @@ class FB2Input(InputFormatPlugin):
             note = notes.get(cite, None)
             if note:
                 c = 1
-                while 'cite%d' % c in all_ids:
+                while f'cite{c}' in all_ids:
                     c += 1
                 if not note.get('id', None):
-                    note.set('id', 'cite%d' % c)
+                    note.set('id', f'cite{c}')
                     all_ids.add(note.get('id'))
                 a.set('href', '#{}'.format(note.get('id')))
         for x in result.xpath('//*[@link_note or @link_cite]'):

src/calibre/ebooks/conversion/plugins/htmlz_input.py

@@ -89,7 +89,7 @@ class HTMLZInput(InputFormatPlugin):
         c = 0
         while os.path.exists(htmlfile):
             c += 1
-            htmlfile = 'index%d.html'%c
+            htmlfile = f'index{c}.html'
         with open(htmlfile, 'wb') as f:
             f.write(html.encode('utf-8'))
         odi = options.debug_pipeline

src/calibre/ebooks/conversion/plugins/rtf_input.py

@@ -141,7 +141,7 @@ class RTFInput(InputFormatPlugin):
             if fmt is None:
                 fmt = 'wmf'
             count += 1
-            name = '%04d.%s' % (count, fmt)
+            name = f'{count:04}.{fmt}'
             with open(name, 'wb') as f:
                 f.write(data)
             imap[count] = name
@@ -243,7 +243,7 @@ class RTFInput(InputFormatPlugin):
             if style not in border_styles:
                 border_styles.append(style)
             idx = border_styles.index(style)
-            cls = 'border_style%d'%idx
+            cls = f'border_style{idx}'
             style_map[cls] = style
             elem.set('class', cls)
         return style_map

src/calibre/ebooks/conversion/plugins/snb_input.py

@@ -90,7 +90,7 @@ class SNBInput(InputFormatPlugin):
                 for ch in toc.find('.//body'):
                     chapterName = ch.text
                     chapterSrc = ch.get('src')
-                    fname = 'ch_%d.htm' % i
+                    fname = f'ch_{i}.htm'
                     data = snbFile.GetFileStream('snbc/' + chapterSrc)
                     if data is None:
                         continue

src/calibre/ebooks/conversion/preprocess.py

@@ -498,7 +498,7 @@ class HTMLPreProcessor:
 
         # search / replace using the sr?_search / sr?_replace options
         for i in range(1, 4):
-            search, replace = 'sr%d_search'%i, 'sr%d_replace'%i
+            search, replace = f'sr{i}_search', f'sr{i}_replace'
             search_pattern = getattr(self.extra_opts, search, '')
             replace_txt = getattr(self.extra_opts, replace, '')
             if search_pattern:
@@ -559,7 +559,7 @@ class HTMLPreProcessor:
                     name, i = None, 0
                     while not name or os.path.exists(os.path.join(odir, name)):
                         i += 1
-                        name = '%04d.html'%i
+                        name = f'{i:04}.html'
                     with open(os.path.join(odir, name), 'wb') as f:
                         f.write(raw.encode('utf-8'))
 

src/calibre/ebooks/conversion/utils.py

@@ -140,7 +140,7 @@ class HeuristicProcessor:
                 name, i = None, 0
                 while not name or os.path.exists(os.path.join(odir, name)):
                     i += 1
-                    name = '%04d.html'%i
+                    name = f'{i:04}.html'
                 with open(os.path.join(odir, name), 'wb') as f:
                     f.write(raw.encode('utf-8'))
 

src/calibre/ebooks/djvu/djvu.py

@@ -45,8 +45,7 @@ class DjvuChunk:
             print('found', self.type, self.subtype, pos, self.size)
         if self.type in b'FORM'.split():
             if verbose > 0:
-                print('processing substuff %d %d (%x)' % (pos, self.dataend,
+                print(f'processing substuff {pos} {self.dataend} ({self.dataend:x})')
-                    self.dataend))
             numchunks = 0
             while pos < self.dataend:
                 x = DjvuChunk(buf, pos, start+self.size, verbose=verbose)
@@ -54,11 +53,10 @@ class DjvuChunk:
                 self._subchunks.append(x)
                 newpos = pos + x.size + x.headersize + (1 if (x.size % 2) else 0)
                 if verbose > 0:
-                    print('newpos %d %d (%x, %x) %d' % (newpos, self.dataend,
+                    print(f'newpos {newpos} {self.dataend} ({newpos:x}, {self.dataend:x}) {x.headersize}')
-                        newpos, self.dataend, x.headersize))
                 pos = newpos
             if verbose > 0:
-                print('                  end of chunk %d (%x)' % (pos, pos))
+                print(f'                  end of chunk {pos} ({pos:x})')
 
     def dump(self, verbose=0, indent=1, out=None, txtout=None, maxlevel=100):
         if out:

src/calibre/ebooks/docx/cleanup.py

@@ -155,7 +155,7 @@ def cleanup_markup(log, root, styles, dest_dir, detect_cover, XPath, uuid):
 
     # Process dir attributes
     class_map = dict(itervalues(styles.classes))
-    parents = ('p', 'div') + tuple('h%d' % i for i in range(1, 7))
+    parents = ('p', 'div') + tuple(f'h{i}' for i in range(1, 7))
     for parent in root.xpath('//*[({})]'.format(' or '.join(f'name()="{t}"' for t in parents))):
         # Ensure that children of rtl parents that are not rtl have an
         # explicit dir set. Also, remove dir from children if it is the same as

src/calibre/ebooks/docx/fields.py

@@ -110,7 +110,7 @@ class Fields:
         c = 0
         while self.index_bookmark_prefix in all_ids:
             c += 1
-            self.index_bookmark_prefix = self.index_bookmark_prefix.replace('-', '%d-' % c)
+            self.index_bookmark_prefix = self.index_bookmark_prefix.replace('-', f'{c}-')
         stack = []
         for elem in self.namespace.XPath(
             '//*[name()="w:p" or name()="w:r" or'
@@ -209,7 +209,7 @@ class Fields:
             def WORD(x):
                 return self.namespace.expand('w:' + x)
             self.index_bookmark_counter += 1
-            bmark = xe['anchor'] = '%s%d' % (self.index_bookmark_prefix, self.index_bookmark_counter)
+            bmark = xe['anchor'] = f'{self.index_bookmark_prefix}{self.index_bookmark_counter}'
             p = field.start.getparent()
             bm = p.makeelement(WORD('bookmarkStart'))
             bm.set(WORD('id'), bmark), bm.set(WORD('name'), bmark)

src/calibre/ebooks/docx/footnotes.py

@@ -48,7 +48,7 @@ class Footnotes:
         note = notes.get(fid, None)
         if note is not None and note.type == 'normal':
             self.counter += 1
-            anchor = 'note_%d' % self.counter
+            anchor = f'note_{self.counter}'
             self.notes[anchor] = (str(self.counter), note)
             return anchor, str(self.counter)
         return None, None

src/calibre/ebooks/docx/images.py

@@ -183,7 +183,7 @@ class Images:
         name = base
         while name in exists:
             n, e = base.rpartition('.')[0::2]
-            name = '%s-%d.%s' % (n, c, e)
+            name = f'{n}-{c}.{e}'
             c += 1
         return name
 
@@ -191,7 +191,7 @@ class Images:
         resized, img = resize_to_fit(raw, max_width, max_height)
         if resized:
             base, ext = os.path.splitext(base)
-            base = base + '-%dx%d%s' % (max_width, max_height, ext)
+            base = base + f'-{max_width}x{max_height}{ext}'
             raw = image_to_data(img, fmt=ext[1:])
         return raw, base, resized
 

src/calibre/ebooks/docx/names.py

@@ -93,7 +93,7 @@ def generate_anchor(name, existing):
     x = y = 'id_' + re.sub(r'[^0-9a-zA-Z_]', '', ascii_text(name)).lstrip('_')
     c = 1
     while y in existing:
-        y = '%s_%d' % (x, c)
+        y = f'{x}_{c}'
         c += 1
     return y
 

src/calibre/ebooks/docx/numbering.py

@@ -40,7 +40,7 @@ def alphabet(val, lower=True):
 alphabet_map = {
     'lower-alpha':alphabet, 'upper-alpha':partial(alphabet, lower=False),
     'lower-roman':lambda x: roman(x).lower(), 'upper-roman':roman,
-    'decimal-leading-zero': lambda x: '0%d' % x
+    'decimal-leading-zero': lambda x: f'0{x}'
 }
 
 
@@ -73,7 +73,7 @@ class Level:
             if x > ilvl or x not in counter:
                 return ''
             val = counter[x] - (0 if x == ilvl else 1)
-            formatter = alphabet_map.get(self.fmt, lambda x: '%d' % x)
+            formatter = alphabet_map.get(self.fmt, lambda x: f'{x}')
             return formatter(val)
         return re.sub(r'%(\d+)', sub, template).rstrip() + '\xa0'
 

src/calibre/ebooks/docx/styles.py

@@ -427,7 +427,7 @@ class Styles:
         ans, _ = self.classes.get(h, (None, None))
         if ans is None:
             self.counter[prefix] += 1
-            ans = '%s_%d' % (prefix, self.counter[prefix])
+            ans = f'{prefix}_{self.counter[prefix]}'
             self.classes[h] = (ans, css)
         return ans
 

src/calibre/ebooks/docx/tables.py

@@ -460,9 +460,9 @@ class Table:
             return (m - (m % n)) // n
         if c is not None:
             odd_column_band = (divisor(c, self.table_style.col_band_size) % 2) == 1
-            overrides.append('band%dVert' % (1 if odd_column_band else 2))
+            overrides.append(f'band{1 if odd_column_band else 2}Vert')
         odd_row_band = (divisor(r, self.table_style.row_band_size) % 2) == 1
-        overrides.append('band%dHorz' % (1 if odd_row_band else 2))
+        overrides.append(f'band{1 if odd_row_band else 2}Horz')
 
         # According to the OOXML spec columns should have higher override
         # priority than rows, but Word seems to do it the other way around.

src/calibre/ebooks/docx/to_html.py

@@ -518,7 +518,7 @@ class Convert:
         m = re.match(r'heading\s+(\d+)$', style.style_name or '', re.IGNORECASE)
         if m is not None:
             n = min(6, max(1, int(m.group(1))))
-            dest.tag = 'h%d' % n
+            dest.tag = f'h{n}'
             dest.set('data-heading-level', str(n))
 
         if style.bidi is True:

src/calibre/ebooks/docx/toc.py

@@ -30,7 +30,7 @@ def from_headings(body, log, namespace, num_levels=3):
     def ensure_id(elem):
         ans = elem.get('id', None)
         if not ans:
-            ans = 'toc_id_%d' % (next(idcount) + 1)
+            ans = f'toc_id_{next(idcount) + 1}'
             elem.set('id', ans)
         return ans
 

src/calibre/ebooks/docx/writer/container.py

@@ -134,7 +134,7 @@ class DocumentRelationships:
     def add_relationship(self, target, rtype, target_mode=None):
         ans = self.get_relationship_id(target, rtype, target_mode)
         if ans is None:
-            ans = 'rId%d' % (len(self.rmap) + 1)
+            ans = f'rId{len(self.rmap) + 1}'
             self.rmap[(target, rtype, target_mode)] = ans
         return ans
 

src/calibre/ebooks/docx/writer/fonts.py

@@ -67,8 +67,8 @@ class FontsManager:
             item = ef['item']
             rid = rel_map.get(item)
             if rid is None:
-                rel_map[item] = rid = 'rId%d' % num
+                rel_map[item] = rid = f'rId{num}'
-                fname = 'fonts/font%d.odttf' % num
+                fname = f'fonts/font{num}.odttf'
                 makeelement(embed_relationships, 'Relationship', Id=rid, Type=self.namespace.names['EMBEDDED_FONT'], Target=fname)
                 font_data_map['word/' + fname] = obfuscate_font_data(item.data, key)
             makeelement(font, 'w:embed' + tag, r_id=rid,

src/calibre/ebooks/docx/writer/links.py

@@ -92,7 +92,7 @@ class LinksManager:
         i, bname = 0, name
         while name in self.used_bookmark_names:
             i += 1
-            name  = bname + ('_%d' % i)
+            name  = bname + f'_{i}'
         self.anchor_map[key] = name
         self.used_bookmark_names.add(name)
         return name

src/calibre/ebooks/docx/writer/lists.py

@@ -84,7 +84,7 @@ class NumberingDefinition:
         makeelement = self.namespace.makeelement
         an = makeelement(parent, 'w:abstractNum', w_abstractNumId=str(self.num_id))
         makeelement(an, 'w:multiLevelType', w_val='hybridMultilevel')
-        makeelement(an, 'w:name', w_val='List %d' % (self.num_id + 1))
+        makeelement(an, 'w:name', w_val=f'List {self.num_id + 1}')
         for level in self.levels:
             level.serialize(an, makeelement)
 

src/calibre/ebooks/docx/writer/styles.py

@@ -744,7 +744,7 @@ class StylesManager:
                 if style.outline_level is None:
                     val = f'Para %0{snum}d' % i
                 else:
-                    val = 'Heading %d' % (style.outline_level + 1)
+                    val = f'Heading {style.outline_level + 1}'
                     heading_styles.append(style)
                 style.id = style.name = val
             style.seq = i
@@ -764,7 +764,7 @@ class StylesManager:
                         ds_counts[run.descendant_style] += run.style_weight
         rnum = len(str(max(1, len(ds_counts) - 1)))
         for i, (text_style, count) in enumerate(ds_counts.most_common()):
-            text_style.id = 'Text%d' % i
+            text_style.id = f'Text{i}'
             text_style.name = f'%0{rnum}d Text' % i
             text_style.seq = i
         self.descendant_text_styles = sorted(descendant_style_map, key=attrgetter('seq'))

src/calibre/ebooks/epub/pages.py

@@ -48,7 +48,7 @@ def add_page_map(opfpath, opts):
     oeb = OEBBook(opfpath)
     selector = XPath(opts.page, namespaces=NSMAP)
     name_for = build_name_for(opts.page_names)
-    idgen = ('calibre-page-%d' % n for n in count(1))
+    idgen = (f'calibre-page-{n}' for n in count(1))
     for item in oeb.spine:
         data = item.data
         for elem in selector(data):

src/calibre/ebooks/epub/periodical.py

@@ -137,7 +137,7 @@ def sony_metadata(oeb):
     for i, section in enumerate(toc):
         if not section.href:
             continue
-        secid = 'section%d'%i
+        secid = f'section{i}'
         sectitle = section.title
         if not sectitle:
             sectitle = _('Unknown')
@@ -170,7 +170,7 @@ def sony_metadata(oeb):
             desc = section.description
             if not desc:
                 desc = ''
-            aid = 'article%d'%j
+            aid = f'article{j}'
 
             entries.append(SONY_ATOM_ENTRY.format(
                 title=xml(atitle),

src/calibre/ebooks/fb2/fb2ml.py

@@ -116,7 +116,7 @@ class FB2MLizer:
         metadata['title'] = self.oeb_book.metadata.title[0].value
         metadata['appname'] = __appname__
         metadata['version'] = __version__
-        metadata['date'] = '%i.%i.%i' % (datetime.now().day, datetime.now().month, datetime.now().year)
+        metadata['date'] = f'{datetime.now().day}.{datetime.now().month}.{datetime.now().year}'
         if self.oeb_book.metadata.language:
             lc = lang_as_iso639_1(self.oeb_book.metadata.language[0].value)
             if not lc:

src/calibre/ebooks/html/input.py

@@ -153,7 +153,7 @@ class HTMLFile:
         return hash(self.path)
 
     def __str__(self):
-        return 'HTMLFile:%d:%s:%r'%(self.level, 'b' if self.is_binary else 'a', self.path)
+        return f"HTMLFile:{self.level}:{'b' if self.is_binary else 'a'}:{self.path!r}"
 
     def __repr__(self):
         return str(self)

src/calibre/ebooks/lit/reader.py

@@ -242,7 +242,7 @@ class UnBinary:
                     if flags & FLAG_ATOM:
                         if not self.tag_atoms or tag not in self.tag_atoms:
                             raise LitError(
-                                'atom tag %d not in atom tag list' % tag)
+                                f'atom tag {tag} not in atom tag list')
                         tag_name = self.tag_atoms[tag]
                         current_map = self.attr_atoms
                     elif tag < len(self.tag_map):
@@ -257,8 +257,7 @@ class UnBinary:
                     buf.write(encode(tag_name))
                 elif flags & FLAG_CLOSING:
                     if depth == 0:
-                        raise LitError('Extra closing tag %s at %d'%(tag_name,
+                        raise LitError(f'Extra closing tag {tag_name} at {self.cpos}')
-                            self.cpos))
                     break
 
             elif state == 'get attr':
@@ -290,7 +289,7 @@ class UnBinary:
                         attr = self.attr_map[oc]
                     if not attr or not isinstance(attr, string_or_bytes):
                         raise LitError(
-                            'Unknown attribute %d in tag %s' % (oc, tag_name))
+                            f'Unknown attribute {oc} in tag {tag_name}')
                     if attr.startswith('%'):
                         in_censorship = True
                         state = 'get value length'
@@ -315,7 +314,7 @@ class UnBinary:
                 if oc == 0xffff:
                     continue
                 if count < 0 or count > (len(bin) - self.cpos):
-                    raise LitError('Invalid character count %d' % count)
+                    raise LitError(f'Invalid character count {count}')
 
             elif state == 'get value':
                 if count == 0xfffe:
@@ -342,7 +341,7 @@ class UnBinary:
             elif state == 'get custom length':
                 count = oc - 1
                 if count <= 0 or count > len(bin)-self.cpos:
-                    raise LitError('Invalid character count %d' % count)
+                    raise LitError(f'Invalid character count {count}')
                 dynamic_tag += 1
                 state = 'get custom'
                 tag_name = ''
@@ -357,7 +356,7 @@ class UnBinary:
             elif state == 'get attr length':
                 count = oc - 1
                 if count <= 0 or count > (len(bin) - self.cpos):
-                    raise LitError('Invalid character count %d' % count)
+                    raise LitError(f'Invalid character count {count}')
                 buf.write(b' ')
                 state = 'get custom attr'
 
@@ -371,7 +370,7 @@ class UnBinary:
             elif state == 'get href length':
                 count = oc - 1
                 if count <= 0 or count > (len(bin) - self.cpos):
-                    raise LitError('Invalid character count %d' % count)
+                    raise LitError(f'Invalid character count {count}')
                 href = ''
                 state = 'get href'
 
@@ -397,8 +396,7 @@ class DirectoryEntry:
         self.size = size
 
     def __repr__(self):
-        return 'DirectoryEntry(name=%s, section=%d, offset=%d, size=%d)' \
+        return f'DirectoryEntry(name={repr(self.name)}, section={self.section}, offset={self.offset}, size={self.size})'
-            % (repr(self.name), self.section, self.offset, self.size)
 
     def __str__(self):
         return repr(self)
@@ -429,9 +427,7 @@ class ManifestItem:
         return self.internal == other
 
     def __repr__(self):
-        return (
+        return f"ManifestItem(internal={self.internal!r}, path={self.path!r}, mime_type={self.mime_type!r}, offset={self.offset}, root={self.root!r}, state={self.state!r})"
-            'ManifestItem(internal=%r, path=%r, mime_type=%r, offset=%d, root=%r, state=%r)'
-            ) % (self.internal, self.path, self.mime_type, self.offset, self.root, self.state)
 
 
 def preserve(function):
@@ -462,7 +458,7 @@ class LitFile:
         if self.magic != b'ITOLITLS':
             raise LitError('Not a valid LIT file')
         if self.version != 1:
-            raise LitError('Unknown LIT version %d' % (self.version,))
+            raise LitError(f'Unknown LIT version {self.version}')
         self.read_secondary_header()
         self.read_header_pieces()
         self.read_section_names()
@@ -553,7 +549,7 @@ class LitFile:
             if blocktype == b'CAOL':
                 if blockver != 2:
                     raise LitError(
-                        'Unknown CAOL block format %d' % blockver)
+                        f'Unknown CAOL block format {blockver}')
                 self.creator_id     = u32(byts[offset+12:])
                 self.entry_chunklen = u32(byts[offset+20:])
                 self.count_chunklen = u32(byts[offset+24:])
@@ -563,7 +559,7 @@ class LitFile:
             elif blocktype == b'ITSF':
                 if blockver != 4:
                     raise LitError(
-                        'Unknown ITSF block format %d' % blockver)
+                        f'Unknown ITSF block format {blockver}')
                 if u32(byts[offset+4+16:]):
                     raise LitError('This file has a 64bit content offset')
                 self.content_offset = u32(byts[offset+16:])

src/calibre/ebooks/lrf/input.py

@@ -138,9 +138,9 @@ class TextBlock(etree.XSLTExtension):
         classes = []
         bs = node.get('blockstyle')
         if bs in self.styles.block_style_map:
-            classes.append('bs%d'%self.styles.block_style_map[bs])
+            classes.append(f'bs{self.styles.block_style_map[bs]}')
         if ts in self.styles.text_style_map:
-            classes.append('ts%d'%self.styles.text_style_map[ts])
+            classes.append(f'ts{self.styles.text_style_map[ts]}')
         if classes:
             root.set('class', ' '.join(classes))
         objid = node.get('objid', None)
@@ -218,7 +218,7 @@ class TextBlock(etree.XSLTExtension):
     def process_container(self, child, tgt):
         idx = self.styles.get_text_styles(child)
         if idx is not None:
-            tgt.set('class', 'ts%d'%idx)
+            tgt.set('class', f'ts{idx}')
         self.parent.append(tgt)
         orig_parent = self.parent
         self.parent = tgt
@@ -305,7 +305,7 @@ class Styles(etree.XSLTExtension):
                 for i, s in enumerate(w):
                     if not s:
                         continue
-                    rsel = '.%s%d'%(sel, i)
+                    rsel = f'.{sel}{i}'
                     s = join(s)
                     f.write(as_bytes(rsel + ' {\n\t' + s + '\n}\n\n'))
 
@@ -331,8 +331,8 @@ class Styles(etree.XSLTExtension):
             if a == 255:
                 return None
             if a == 0:
-                return 'rgb(%d,%d,%d)'%(r,g,b)
+                return f'rgb({r},{g},{b})'
-            return 'rgba(%d,%d,%d,%f)'%(r,g,b,1.-a/255.)
+            return f'rgba({r},{g},{b},{1.0 - a / 255.0:f})'
         except:
             return None
 

src/calibre/ebooks/lrf/lrfparser.py

@@ -116,7 +116,7 @@ class LRFDocument(LRFMetaFile):
                 close = '</Main>\n'
                 pt_id = page_tree.id
             else:
-                pages += '<PageTree objid="%d">\n'%(page_tree.id,)
+                pages += f'<PageTree objid="{page_tree.id}">\n'
                 close = '</PageTree>\n'
             for page in page_tree:
                 pages += str(page)

src/calibre/ebooks/lrf/objects.py

@@ -261,7 +261,7 @@ class Color:
         return (self.r, self.g, self.b, 0xff-self.a)[i]  # In Qt 0xff is opaque while in LRS 0x00 is opaque
 
     def to_html(self):
-        return 'rgb(%d, %d, %d)'%(self.r, self.g, self.b)
+        return f'rgb({self.r}, {self.g}, {self.b})'
 
 
 class EmptyPageElement:
@@ -303,7 +303,7 @@ class Wait(EmptyPageElement):
         self.time = time
 
     def __str__(self):
-        return '\n<Wait time="%d" />\n'%(self.time)
+        return f'\n<Wait time="{self.time}" />\n'
 
 
 class Locate(EmptyPageElement):
@@ -323,8 +323,7 @@ class BlockSpace(EmptyPageElement):
         self.xspace, self.yspace = xspace, yspace
 
     def __str__(self):
-        return '\n<BlockSpace xspace="%d" yspace="%d" />\n'%\
+        return f'\n<BlockSpace xspace="{self.xspace}" yspace="{self.yspace}" />\n'
-                (self.xspace, self.yspace)
 
 
 class Page(LRFStream):
@@ -420,7 +419,7 @@ class Page(LRFStream):
         yield from self.content
 
     def __str__(self):
-        s = '\n<Page pagestyle="%d" objid="%d">\n'%(self.style_id, self.id)
+        s = f'\n<Page pagestyle="{self.style_id}" objid="{self.id}">\n'
         for i in self:
             s += str(i)
         s += '\n</Page>\n'
@@ -470,11 +469,11 @@ class BlockAttr(StyleObject, LRFObject):
             margin = str(obj.sidemargin) + 'px'
             ans += item('margin-left: {m}; margin-right: {m};'.format(**dict(m=margin)))
         if hasattr(obj, 'topskip'):
-            ans += item('margin-top: %dpx;'%obj.topskip)
+            ans += item(f'margin-top: {obj.topskip}px;')
         if hasattr(obj, 'footskip'):
-            ans += item('margin-bottom: %dpx;'%obj.footskip)
+            ans += item(f'margin-bottom: {obj.footskip}px;')
         if hasattr(obj, 'framewidth'):
-            ans += item('border: solid %dpx'%obj.framewidth)
+            ans += item(f'border: solid {obj.framewidth}px')
         if hasattr(obj, 'framecolor') and obj.framecolor.a < 255:
             ans += item(f'border-color: {obj.framecolor.to_html()};')
         if hasattr(obj, 'bgcolor') and obj.bgcolor.a < 255:
@@ -602,9 +601,9 @@ class Block(LRFStream, TextCSS):
                 self.attrs[attr] = getattr(self, attr)
 
     def __str__(self):
-        s = '\n<%s objid="%d" blockstyle="%s" '%(self.name, self.id, getattr(self, 'style_id', ''))
+        s = f"\n<{self.name} objid=\"{self.id}\" blockstyle=\"{getattr(self, 'style_id', '')}\" "
         if hasattr(self, 'textstyle_id'):
-            s += 'textstyle="%d" '%(self.textstyle_id,)
+            s += f'textstyle="{self.textstyle_id}" '
         for attr in self.attrs:
             s += f'{attr}="{self.attrs[attr]}" '
         if self.name != 'ImageBlock':
@@ -933,8 +932,7 @@ class Image(LRFObject):
     data = property(fget=lambda self: self._document.objects[self.refstream].stream)
 
     def __str__(self):
-        return '<Image objid="%s" x0="%d" y0="%d" x1="%d" y1="%d" xsize="%d" ysize="%d" refstream="%d" />\n'%\
+        return f'<Image objid="{self.id}" x0="{self.x0}" y0="{self.y0}" x1="{self.x1}" y1="{self.y1}" xsize="{self.xsize}" ysize="{self.ysize}" refstream="{self.refstream}" />\n'
-        (self.id, self.x0, self.y0, self.x1, self.y1, self.xsize, self.ysize, self.refstream)
 
 
 class PutObj(EmptyPageElement):
@@ -944,7 +942,7 @@ class PutObj(EmptyPageElement):
         self.object = objects[refobj]
 
     def __str__(self):
-        return '<PutObj x1="%d" y1="%d" refobj="%d" />'%(self.x1, self.y1, self.refobj)
+        return f'<PutObj x1="{self.x1}" y1="{self.y1}" refobj="{self.refobj}" />'
 
 
 class Canvas(LRFStream):

src/calibre/ebooks/lrf/pylrs/pylrs.py

@@ -341,7 +341,7 @@ class LrsObject:
         if labelName is None:
             labelName = name
         if labelDecorate:
-            label = '%s.%d' % (labelName, self.objId)
+            label = f'{labelName}.{self.objId}'
         else:
             label = str(self.objId)
         element.attrib[objlabel] = label

src/calibre/ebooks/lrf/tags.py

@@ -188,7 +188,7 @@ class Tag:
         self.offset = stream.tell()
         tag_id = struct.unpack('<BB', stream.read(2))
         if tag_id[1] != 0xF5:
-            raise LRFParseError('Bad tag ID %02X at %d'%(tag_id[1], self.offset))
+            raise LRFParseError(f'Bad tag ID {tag_id[1]:02X} at {self.offset}')
         if tag_id[0] not in self.__class__.tags:
             raise LRFParseError(f'Unknown tag ID: F5{tag_id[0]:02X}')
 

src/calibre/ebooks/metadata/mobi.py

@@ -227,7 +227,7 @@ class MetadataUpdater:
         # Fetch the existing title
         title_offset, = unpack('>L', self.record0[0x54:0x58])
         title_length, = unpack('>L', self.record0[0x58:0x5c])
-        title_in_file, = unpack('%ds' % (title_length), self.record0[title_offset:title_offset + title_length])
+        title_in_file, = unpack(f'{title_length}s', self.record0[title_offset:title_offset + title_length])
 
         # Adjust length to accommodate PrimaryINDX if necessary
         mobi_header_length, = unpack('>L', self.record0[0x14:0x18])

src/calibre/ebooks/metadata/opf2.py

@@ -226,7 +226,7 @@ class ManifestItem(Resource):  # {{{
             return self.href()
         if index == 1:
             return self.media_type
-        raise IndexError('%d out of bounds.'%index)
+        raise IndexError(f'{index} out of bounds.')
 
 # }}}
 
@@ -237,7 +237,7 @@ class Manifest(ResourceCollection):  # {{{
         self.append(ManifestItem.from_opf_manifest_item(item, dir))
         id = item.get('id', '')
         if not id:
-            id = 'id%d'%self.next_id
+            id = f'id{self.next_id}'
         self[-1].id = id
         self.next_id += 1
 
@@ -261,7 +261,7 @@ class Manifest(ResourceCollection):  # {{{
             mi = ManifestItem(path, is_path=True)
             if mt:
                 mi.mime_type = mt
-            mi.id = 'id%d'%m.next_id
+            mi.id = f'id{m.next_id}'
             m.next_id += 1
             m.append(mi)
         return m
@@ -270,7 +270,7 @@ class Manifest(ResourceCollection):  # {{{
         mi = ManifestItem(path, is_path=True)
         if mime_type:
             mi.mime_type = mime_type
-        mi.id = 'id%d'%self.next_id
+        mi.id = f'id{self.next_id}'
         self.next_id += 1
         self.append(mi)
         return mi.id
@@ -787,7 +787,7 @@ class OPF:  # {{{
         c = 1
         while manifest_id in ids:
             c += 1
-            manifest_id = 'id%d'%c
+            manifest_id = f'id{c}'
         if not media_type:
             media_type = 'application/xhtml+xml'
         ans = etree.Element('{{{}}}item'.format(self.NAMESPACES['opf']),
@@ -801,7 +801,7 @@ class OPF:  # {{{
     def replace_manifest_item(self, item, items):
         items = [self.create_manifest_item(*i) for i in items]
         for i, item2 in enumerate(items):
-            item2.set('id', item.get('id')+'.%d'%(i+1))
+            item2.set('id', item.get('id')+f'.{i + 1}')
         manifest = item.getparent()
         index = manifest.index(item)
         manifest[index:index+1] = items

src/calibre/ebooks/metadata/pdf.py

@@ -39,7 +39,7 @@ def read_info(outputdir, get_cover):
     try:
         raw = subprocess.check_output([pdfinfo, '-enc', 'UTF-8', '-isodates', 'src.pdf'])
     except subprocess.CalledProcessError as e:
-        prints('pdfinfo errored out with return code: %d'%e.returncode)
+        prints(f'pdfinfo errored out with return code: {e.returncode}')
         return None
     try:
         info_raw = raw.decode('utf-8')
@@ -63,7 +63,7 @@ def read_info(outputdir, get_cover):
     try:
         raw = subprocess.check_output([pdfinfo, '-meta', 'src.pdf']).strip()
     except subprocess.CalledProcessError as e:
-        prints('pdfinfo failed to read XML metadata with return code: %d'%e.returncode)
+        prints(f'pdfinfo failed to read XML metadata with return code: {e.returncode}')
     else:
         parts = re.split(br'^Metadata:', raw, 1, flags=re.MULTILINE)
         if len(parts) > 1:
@@ -77,7 +77,7 @@ def read_info(outputdir, get_cover):
             subprocess.check_call([pdftoppm, '-singlefile', '-jpeg', '-cropbox',
                 'src.pdf', 'cover'])
         except subprocess.CalledProcessError as e:
-            prints('pdftoppm errored out with return code: %d'%e.returncode)
+            prints(f'pdftoppm errored out with return code: {e.returncode}')
 
     return ans
 

src/calibre/ebooks/metadata/toc.py

@@ -263,7 +263,7 @@ class TOC(list):
             if not text:
                 text = ''
             c[1] += 1
-            item_id = 'num_%d'%c[1]
+            item_id = f'num_{c[1]}'
             text = clean_xml_chars(text)
             elem = E.navPoint(
                     E.navLabel(E.text(re.sub(r'\s+', ' ', text))),

src/calibre/ebooks/metadata/topaz.py

@@ -148,7 +148,7 @@ class MetadataUpdater:
         for tag in self.topaz_headers:
             print(f'{tag}: ')
             num_recs = len(self.topaz_headers[tag]['blocks'])
-            print(' num_recs: %d' % num_recs)
+            print(f' num_recs: {num_recs}')
             if num_recs:
                 print(' starting offset: 0x{:x}'.format(self.topaz_headers[tag]['blocks'][0]['offset']))
 

src/calibre/ebooks/metadata/utils.py

@@ -81,7 +81,7 @@ def ensure_unique(template, existing):
     c = 0
     while q in existing:
         c += 1
-        q = '%s-%d%s' % (b, c, e)
+        q = f'{b}-{c}{e}'
     return q
 
 

src/calibre/ebooks/metadata/xmp.py

@@ -585,7 +585,7 @@ def find_nsmap(elems):
                 ans[pp] = ns
             else:
                 i += 1
-                ans['ns%d' % i] = ns
+                ans[f'ns{i}'] = ns
     return ans
 
 

src/calibre/ebooks/mobi/debug/containers.py

@@ -46,19 +46,19 @@ class ContainerHeader:
     def __str__(self):
         ans = [('*'*10) + ' Container Header ' + ('*'*10)]
         a = ans.append
-        a('Record size: %d' % self.record_size)
+        a(f'Record size: {self.record_size}')
-        a('Type: %d' % self.type)
+        a(f'Type: {self.type}')
-        a('Total number of records in this container: %d' % self.count)
+        a(f'Total number of records in this container: {self.count}')
         a(f'Encoding: {self.encoding}')
         a(f'Unknowns1: {self.unknowns1}')
-        a('Num of resource records: %d' % self.num_of_resource_records)
+        a(f'Num of resource records: {self.num_of_resource_records}')
-        a('Num of non-dummy resource records: %d' % self.num_of_non_dummy_resource_records)
+        a(f'Num of non-dummy resource records: {self.num_of_non_dummy_resource_records}')
-        a('Offset to href record: %d' % self.offset_to_href_record)
+        a(f'Offset to href record: {self.offset_to_href_record}')
         a(f'Unknowns2: {self.unknowns2}')
-        a('Header length: %d' % self.header_length)
+        a(f'Header length: {self.header_length}')
         a(f'Title Length: {self.title_length}')
         a(f'hrefs: {self.hrefs}')
-        a('Null bytes after EXTH: %d' % self.null_bytes_after_exth)
+        a(f'Null bytes after EXTH: {self.null_bytes_after_exth}')
         if len(self.bytes_after_exth) != self.null_bytes_after_exth:
             a('Non-null bytes present after EXTH header!!!!')
         return '\n'.join(ans) + '\n\n' + str(self.exth) + '\n\n' + (f'Title: {self.title}')

src/calibre/ebooks/mobi/debug/headers.py

@@ -116,8 +116,7 @@ class Record:  # {{{
 
     @property
     def header(self):
-        return 'Offset: %d Flags: %d UID: %d First 4 bytes: %r Size: %d'%(self.offset, self.flags,
+        return f'Offset: {self.offset} Flags: {self.flags} UID: {self.uid} First 4 bytes: {self.raw[:4]!r} Size: {len(self.raw)}'
-                self.uid, self.raw[:4], len(self.raw))
 # }}}
 
 
@@ -213,7 +212,7 @@ class EXTHRecord:
             self.data = binascii.hexlify(self.data)
 
     def __str__(self):
-        return '%s (%d): %r'%(self.name, self.type, self.data)
+        return f'{self.name} ({self.type}): {self.data!r}'
 
 
 class EXTHHeader:
@@ -254,8 +253,8 @@ class EXTHHeader:
 
     def __str__(self):
         ans = ['*'*20 + ' EXTH Header '+ '*'*20]
-        ans.append('EXTH header length: %d'%self.length)
+        ans.append(f'EXTH header length: {self.length}')
-        ans.append('Number of EXTH records: %d'%self.count)
+        ans.append(f'Number of EXTH records: {self.count}')
         ans.append('EXTH records...')
         for r in self.records:
             ans.append(str(r))
@@ -416,7 +415,7 @@ class MOBIHeader:  # {{{
                 self.last_resource_record = self.exth.kf8_header_index - 2
 
     def __str__(self):
-        ans = ['*'*20 + ' MOBI %d Header '%self.file_version+ '*'*20]
+        ans = ['*'*20 + f' MOBI {self.file_version} Header '+ '*'*20]
 
         a = ans.append
 
@@ -427,39 +426,39 @@ class MOBIHeader:  # {{{
         def r(d, attr):
             x = getattr(self, attr)
             if attr in self.relative_records and x != NULL_INDEX:
-                a('%s: Absolute: %d Relative: %d'%(d, x, x-self.header_offset))
+                a(f'{d}: Absolute: {x} Relative: {x - self.header_offset}')
             else:
                 i(d, x)
 
         a(f'Compression: {self.compression}')
         a(f'Unused: {self.unused!r}')
-        a('Text length: %d'%self.text_length)
+        a(f'Text length: {self.text_length}')
-        a('Number of text records: %d'%self.number_of_text_records)
+        a(f'Number of text records: {self.number_of_text_records}')
-        a('Text record size: %d'%self.text_record_size)
+        a(f'Text record size: {self.text_record_size}')
         a(f'Encryption: {self.encryption_type}')
         a(f'Unknown: {self.unknown!r}')
         a(f'Identifier: {self.identifier!r}')
-        a('Header length: %d'% self.length)
+        a(f'Header length: {self.length}')
         a(f'Type: {self.type}')
         a(f'Encoding: {self.encoding}')
         a(f'UID: {self.uid!r}')
-        a('File version: %d'%self.file_version)
+        a(f'File version: {self.file_version}')
         r('Meta Orth Index', 'meta_orth_indx')
         r('Meta Infl Index', 'meta_infl_indx')
         r('Secondary index record', 'secondary_index_record')
         a(f'Reserved: {self.reserved!r}')
         r('First non-book record', 'first_non_book_record')
-        a('Full name offset: %d'%self.fullname_offset)
+        a(f'Full name offset: {self.fullname_offset}')
-        a('Full name length: %d bytes'%self.fullname_length)
+        a(f'Full name length: {self.fullname_length} bytes')
         a(f'Langcode: {self.locale_raw!r}')
         a(f'Language: {self.language}')
         a(f'Sub language: {self.sublanguage}')
         a(f'Input language: {self.input_language!r}')
         a(f'Output language: {self.output_langauage!r}')
-        a('Min version: %d'%self.min_version)
+        a(f'Min version: {self.min_version}')
         r('First Image index', 'first_image_index')
         r('Huffman record offset', 'huffman_record_offset')
-        a('Huffman record count: %d'%self.huffman_record_count)
+        a(f'Huffman record count: {self.huffman_record_count}')
         r('Huffman table offset', 'datp_record_offset')
         a(f'Huffman table length: {self.datp_record_count!r}')
         a(f'EXTH flags: {bin(self.exth_flags)[2:]} ({self.has_exth})')
@@ -472,18 +471,18 @@ class MOBIHeader:  # {{{
         if self.has_extra_data_flags:
             a(f'Unknown4: {self.unknown4!r}')
             if hasattr(self, 'first_text_record'):
-                a('First content record: %d'%self.first_text_record)
+                a(f'First content record: {self.first_text_record}')
-                a('Last content record: %d'%self.last_text_record)
+                a(f'Last content record: {self.last_text_record}')
             else:
                 r('FDST Index', 'fdst_idx')
-            a('FDST Count: %d'% self.fdst_count)
+            a(f'FDST Count: {self.fdst_count}')
             r('FCIS number', 'fcis_number')
-            a('FCIS count: %d'% self.fcis_count)
+            a(f'FCIS count: {self.fcis_count}')
             r('FLIS number', 'flis_number')
-            a('FLIS count: %d'% self.flis_count)
+            a(f'FLIS count: {self.flis_count}')
             a(f'Unknown6: {self.unknown6!r}')
             r('SRCS record index', 'srcs_record_index')
-            a('Number of SRCS records?: %d'%self.num_srcs_records)
+            a(f'Number of SRCS records?: {self.num_srcs_records}')
             a(f'Unknown7: {self.unknown7!r}')
             a(f'Extra data flags: {bin(self.extra_data_flags)} (has multibyte: {self.has_multibytes}) '
                 f'(has indexing: {self.has_indexing_bytes}) (has uncrossable breaks: {self.has_uncrossable_breaks})')
@@ -502,8 +501,7 @@ class MOBIHeader:  # {{{
             ans += '\n\n' + str(self.exth)
             ans += f'\n\nBytes after EXTH ({len(self.bytes_after_exth)} bytes): {format_bytes(self.bytes_after_exth)}'
 
-        ans += '\nNumber of bytes after full name: %d' % (len(self.raw) - (self.fullname_offset +
+        ans += f'\nNumber of bytes after full name: {len(self.raw) - (self.fullname_offset + self.fullname_length)}'
-                self.fullname_length))
 
         ans += f'\nRecord 0 length: {len(self.raw)}'
         return ans
@@ -599,13 +597,12 @@ class TextRecord:  # {{{
 
         for typ, val in iteritems(self.trailing_data):
             if isinstance(typ, numbers.Integral):
-                print('Record %d has unknown trailing data of type: %d : %r'%
+                print(f'Record {idx} has unknown trailing data of type: {typ} : {val!r}')
-                        (idx, typ, val))
 
         self.idx = idx
 
     def dump(self, folder):
-        name = '%06d'%self.idx
+        name = f'{self.idx:06}'
         with open(os.path.join(folder, name+'.txt'), 'wb') as f:
             f.write(self.raw)
         with open(os.path.join(folder, name+'.trailing_data'), 'wb') as f:

src/calibre/ebooks/mobi/debug/index.py

@@ -100,14 +100,14 @@ class Index:
         ans.extend(['', ''])
         ans += ['*'*10 + f' Index Record Headers ({len(self.index_headers)} records) ' + '*'*10]
         for i, header in enumerate(self.index_headers):
-            ans += ['*'*10 + ' Index Record %d ' % i + '*'*10]
+            ans += ['*'*10 + f' Index Record {i} ' + '*'*10]
             for field in INDEX_HEADER_FIELDS:
                 a('%-12s: %r'%(FIELD_NAMES.get(field, field), header[field]))
 
         if self.cncx:
             a('*'*10 + ' CNCX ' + '*'*10)
             for offset, val in iteritems(self.cncx):
-                a('%10s: %s'%(offset, val))
+                a(f'{offset:10}: {val}')
             ans.extend(['', ''])
 
         if self.table is not None:

src/calibre/ebooks/mobi/debug/mobi6.py

@@ -30,8 +30,7 @@ class TagX:  # {{{
         self.is_eof = (self.eof == 1 and self.tag == 0 and self.num_values == 0 and self.bitmask == 0)
 
     def __repr__(self):
-        return 'TAGX(tag=%02d, num_values=%d, bitmask=%r, eof=%d)' % (self.tag,
+        return f'TAGX(tag={self.tag:02}, num_values={self.num_values}, bitmask={bin(self.bitmask)!r}, eof={self.eof})'
-                self.num_values, bin(self.bitmask), self.eof)
 # }}}
 
 
@@ -55,7 +54,7 @@ class SecondaryIndexHeader:  # {{{
                 'cp1252'}.get(self.index_encoding_num, 'unknown')
         if self.index_encoding == 'unknown':
             raise ValueError(
-                'Unknown index encoding: %d'%self.index_encoding_num)
+                f'Unknown index encoding: {self.index_encoding_num}')
         self.unknown2 = raw[32:36]
         self.num_index_entries, = struct.unpack('>I', raw[36:40])
         self.ordt_start, = struct.unpack('>I', raw[40:44])
@@ -102,30 +101,29 @@ class SecondaryIndexHeader:  # {{{
             a('Unknown: %r (%d bytes) (All zeros: %r)'%(w,
                 len(w), not bool(w.replace(b'\0', b''))))
 
-        a('Header length: %d'%self.header_length)
+        a(f'Header length: {self.header_length}')
         u(self.unknown1)
-        a('Index Type: %s (%d)'%(self.index_type_desc, self.index_type))
+        a(f'Index Type: {self.index_type_desc} ({self.index_type})')
-        a('Offset to IDXT start: %d'%self.idxt_start)
+        a(f'Offset to IDXT start: {self.idxt_start}')
-        a('Number of index records: %d'%self.index_count)
+        a(f'Number of index records: {self.index_count}')
-        a('Index encoding: %s (%d)'%(self.index_encoding,
+        a(f'Index encoding: {self.index_encoding} ({self.index_encoding_num})')
-                self.index_encoding_num))
         u(self.unknown2)
-        a('Number of index entries: %d'% self.num_index_entries)
+        a(f'Number of index entries: {self.num_index_entries}')
-        a('ORDT start: %d'%self.ordt_start)
+        a(f'ORDT start: {self.ordt_start}')
-        a('LIGT start: %d'%self.ligt_start)
+        a(f'LIGT start: {self.ligt_start}')
-        a('Number of LIGT entries: %d'%self.num_of_ligt_entries)
+        a(f'Number of LIGT entries: {self.num_of_ligt_entries}')
-        a('Number of cncx blocks: %d'%self.num_of_cncx_blocks)
+        a(f'Number of cncx blocks: {self.num_of_cncx_blocks}')
         u(self.unknown3)
-        a('TAGX offset: %d'%self.tagx_offset)
+        a(f'TAGX offset: {self.tagx_offset}')
         u(self.unknown4)
         a('\n\n')
-        a('*'*20 + ' TAGX Header (%d bytes)'%self.tagx_header_length+ '*'*20)
+        a('*'*20 + f' TAGX Header ({self.tagx_header_length} bytes)'+ '*'*20)
-        a('Header length: %d'%self.tagx_header_length)
+        a(f'Header length: {self.tagx_header_length}')
-        a('Control byte count: %d'%self.tagx_control_byte_count)
+        a(f'Control byte count: {self.tagx_control_byte_count}')
         for i in self.tagx_entries:
             a('\t' + repr(i))
         a(f'Index of last IndexEntry in secondary index record: {self.last_entry}')
-        a('Number of entries in the NCX: %d'% self.ncx_count)
+        a(f'Number of entries in the NCX: {self.ncx_count}')
 
         return '\n'.join(ans)
 
@@ -154,7 +152,7 @@ class IndexHeader:  # {{{
                 'cp1252'}.get(self.index_encoding_num, 'unknown')
         if self.index_encoding == 'unknown':
             raise ValueError(
-                'Unknown index encoding: %d'%self.index_encoding_num)
+                f'Unknown index encoding: {self.index_encoding_num}')
         self.possibly_language = raw[32:36]
         self.num_index_entries, = struct.unpack('>I', raw[36:40])
         self.ordt_start, = struct.unpack('>I', raw[40:44])
@@ -204,31 +202,30 @@ class IndexHeader:  # {{{
             a('Unknown: %r (%d bytes) (All zeros: %r)'%(w,
                 len(w), not bool(w.replace(b'\0', b''))))
 
-        a('Header length: %d'%self.header_length)
+        a(f'Header length: {self.header_length}')
         u(self.unknown1)
-        a('Header type: %d'%self.header_type)
+        a(f'Header type: {self.header_type}')
-        a('Index Type: %s (%d)'%(self.index_type_desc, self.index_type))
+        a(f'Index Type: {self.index_type_desc} ({self.index_type})')
-        a('Offset to IDXT start: %d'%self.idxt_start)
+        a(f'Offset to IDXT start: {self.idxt_start}')
-        a('Number of index records: %d'%self.index_count)
+        a(f'Number of index records: {self.index_count}')
-        a('Index encoding: %s (%d)'%(self.index_encoding,
+        a(f'Index encoding: {self.index_encoding} ({self.index_encoding_num})')
-                self.index_encoding_num))
         a(f'Unknown (possibly language?): {self.possibly_language!r}')
-        a('Number of index entries: %d'% self.num_index_entries)
+        a(f'Number of index entries: {self.num_index_entries}')
-        a('ORDT start: %d'%self.ordt_start)
+        a(f'ORDT start: {self.ordt_start}')
-        a('LIGT start: %d'%self.ligt_start)
+        a(f'LIGT start: {self.ligt_start}')
-        a('Number of LIGT entries: %d'%self.num_of_ligt_entries)
+        a(f'Number of LIGT entries: {self.num_of_ligt_entries}')
-        a('Number of cncx blocks: %d'%self.num_of_cncx_blocks)
+        a(f'Number of cncx blocks: {self.num_of_cncx_blocks}')
         u(self.unknown2)
-        a('TAGX offset: %d'%self.tagx_offset)
+        a(f'TAGX offset: {self.tagx_offset}')
         u(self.unknown3)
         a('\n\n')
-        a('*'*20 + ' TAGX Header (%d bytes)'%self.tagx_header_length+ '*'*20)
+        a('*'*20 + f' TAGX Header ({self.tagx_header_length} bytes)'+ '*'*20)
-        a('Header length: %d'%self.tagx_header_length)
+        a(f'Header length: {self.tagx_header_length}')
-        a('Control byte count: %d'%self.tagx_control_byte_count)
+        a(f'Control byte count: {self.tagx_control_byte_count}')
         for i in self.tagx_entries:
             a('\t' + repr(i))
         a(f'Index of last IndexEntry in primary index record: {self.last_entry}')
-        a('Number of entries in the NCX: %d'% self.ncx_count)
+        a(f'Number of entries in the NCX: {self.ncx_count}')
 
         return '\n'.join(ans)
 # }}}
@@ -275,7 +272,7 @@ class Tag:  # {{{
             self.attr, self.desc = self.TAG_MAP[tag_type]
         else:
             print('Unknown tag value: %s')
-            self.desc = '??Unknown (tag value: %d)'%tag_type
+            self.desc = f'??Unknown (tag value: {tag_type})'
             self.attr = 'unknown'
 
         if '_offset' in self.attr:
@@ -368,8 +365,7 @@ class IndexEntry:  # {{{
             if tag.value is not None:
                 ans.append('\t'+str(tag))
         if self.first_child_index != -1:
-            ans.append('\tNumber of children: %d'%(self.last_child_index -
+            ans.append(f'\tNumber of children: {self.last_child_index - self.first_child_index + 1}')
-                self.first_child_index + 1))
         return '\n'.join(ans)
 
 # }}}
@@ -458,8 +454,7 @@ class CNCX:  # {{{
                     except:
                         byts = raw[pos:]
                         r = format_bytes(byts)
-                        print('CNCX entry at offset %d has unknown format %s'%(
+                        print(f'CNCX entry at offset {pos + record_offset} has unknown format {r}')
-                            pos+record_offset, r))
                         self.records[pos+record_offset] = r
                         pos = len(raw)
                 pos += consumed+length
@@ -471,7 +466,7 @@ class CNCX:  # {{{
     def __str__(self):
         ans = ['*'*20 + f' cncx ({len(self.records)} strings) '+ '*'*20]
         for k, v in iteritems(self.records):
-            ans.append('%10d : %s'%(k, v))
+            ans.append(f'{k:10} : {v}')
         return '\n'.join(ans)
 
 # }}}
@@ -485,7 +480,7 @@ class ImageRecord:  # {{{
         self.idx = idx
 
     def dump(self, folder):
-        name = '%06d'%self.idx
+        name = f'{self.idx:06}'
         with open(os.path.join(folder, name+'.'+self.fmt), 'wb') as f:
             f.write(self.raw)
 
@@ -497,7 +492,7 @@ class BinaryRecord:  # {{{
     def __init__(self, idx, record):
         self.raw = record.raw
         sig = self.raw[:4]
-        name = '%06d'%idx
+        name = f'{idx:06}'
         if sig in {b'FCIS', b'FLIS', b'SRCS', b'DATP', b'RESC', b'BOUN',
                 b'FDST', b'AUDI', b'VIDE', b'CRES', b'CONT', b'CMET'}:
             name += '-' + sig.decode('ascii')
@@ -516,7 +511,7 @@ class FontRecord:  # {{{
 
     def __init__(self, idx, record):
         self.raw = record.raw
-        name = '%06d'%idx
+        name = f'{idx:06}'
         self.font = read_font_record(self.raw)
         if self.font['err']:
             raise ValueError('Failed to read font record: {} Headers: {}'.format(
@@ -564,7 +559,7 @@ class TBSIndexing:  # {{{
         for i in self.indices:
             if i.index in {idx, str(idx)}:
                 return i
-        raise IndexError('Index %d not found'%idx)
+        raise IndexError(f'Index {idx} not found')
 
     def __str__(self):
         ans = ['*'*20 + f' TBS Indexing ({len(self.record_indices)} records) '+ '*'*20]
@@ -580,13 +575,12 @@ class TBSIndexing:  # {{{
                 continue
             types[tbs_type] += strings
         for typ, strings in iteritems(types):
-            with open(os.path.join(bdir, 'tbs_type_%d.txt'%typ), 'wb') as f:
+            with open(os.path.join(bdir, f'tbs_type_{typ}.txt'), 'wb') as f:
                 f.write(as_bytes('\n'.join(strings)))
 
     def dump_record(self, r, dat):
         ans = []
-        ans.append('\nRecord #%d: Starts at: %d Ends at: %d'%(r.idx,
+        ans.append(f"\nRecord #{r.idx}: Starts at: {dat['geom'][0]} Ends at: {dat['geom'][1]}")
-            dat['geom'][0], dat['geom'][1]))
         s, e, c = dat['starts'], dat['ends'], dat['complete']
         ans.append(('\tContains: %d index entries '
             '(%d ends, %d complete, %d starts)')%tuple(map(len, (s+e+c, e,
@@ -597,9 +591,7 @@ class TBSIndexing:  # {{{
             if entries:
                 ans.append(f'\t{typ}:')
                 for x in entries:
-                    ans.append(('\t\tIndex Entry: %s (Parent index: %s, '
+                    ans.append(f"\t\tIndex Entry: {x.index} (Parent index: {x.parent_index}, Depth: {x.depth}, Offset: {x.offset}, Size: {x.size}) [{x.label}]")
-                            'Depth: %d, Offset: %d, Size: %d) [%s]')%(
-                        x.index, x.parent_index, x.depth, x.offset, x.size, x.label))
 
         def bin4(num):
             ans = bin(num)[2:]
@@ -615,8 +607,8 @@ class TBSIndexing:  # {{{
             byts = byts[consumed:]
             for k in extra:
                 tbs_type |= k
-            ans.append('\nTBS: %d (%s)'%(tbs_type, bin4(tbs_type)))
+            ans.append(f'\nTBS: {tbs_type} ({bin4(tbs_type)})')
-            ans.append('Outermost index: %d'%outermost_index)
+            ans.append(f'Outermost index: {outermost_index}')
             ans.append(f'Unknown extra start bytes: {repr_extra(extra)}')
             if is_periodical:  # Hierarchical periodical
                 try:
@@ -626,7 +618,7 @@ class TBSIndexing:  # {{{
                     import traceback
                     traceback.print_exc()
                     a = []
-                    print('Failed to decode TBS bytes for record: %d'%r.idx)
+                    print(f'Failed to decode TBS bytes for record: {r.idx}')
                 ans += a
             if byts:
                 sbyts = tuple(hex(b)[2:] for b in byts)
@@ -654,35 +646,25 @@ class TBSIndexing:  # {{{
                         raise ValueError('Dont know how to interpret flags'
                                 f' {extra!r} while reading section transitions')
                     nsi = self.get_index(psi.index+1)
-                    ans.append('Last article in this record of section %d'
+                    ans.append(f'Last article in this record of section {psi.index} (relative to next section index [{nsi.index}]): {ai} [{ai + nsi.index} absolute index]')
-                            ' (relative to next section index [%d]): '
-                            '%d [%d absolute index]'%(psi.index, nsi.index, ai,
-                                ai+nsi.index))
                     psi = nsi
                     continue
 
-                ans.append('First article in this record of section %d'
+                ans.append(f'First article in this record of section {psi.index} (relative to its parent section): {ai} [{ai + psi.index} absolute index]')
-                        ' (relative to its parent section): '
-                        '%d [%d absolute index]'%(psi.index, ai, ai+psi.index))
 
                 num = extra.get(0b0100, None)
                 if num is None:
-                    msg = ('The section %d has at most one article'
+                    msg = f"The section {psi.index} has at most one article in this record"
-                            ' in this record')%psi.index
                 else:
-                    msg = ('Number of articles in this record of '
+                    msg = f"Number of articles in this record of section {psi.index}: {num}"
-                        'section %d: %d')%(psi.index, num)
                 ans.append(msg)
 
                 offset = extra.get(0b0001, None)
                 if offset is not None:
                     if offset == 0:
-                        ans.append('This record is spanned by the article:'
+                        ans.append(f'This record is spanned by the article:{ai + psi.index}')
-                                '%d'%(ai+psi.index))
                     else:
-                        ans.append('->Offset to start of next section (%d) from start'
+                        ans.append(f'->Offset to start of next section ({psi.index + 1}) from start of record: {offset} [{offset + record_offset} absolute offset]')
-                            ' of record: %d [%d absolute offset]'%(psi.index+1,
-                                offset, offset+record_offset))
             return byts
         # }}}
 
@@ -698,8 +680,7 @@ class TBSIndexing:  # {{{
                     f' {si.index}')
             if 0b0100 in extra:
                 num = extra[0b0100]
-                ans.append('The number of articles from the section %d'
+                ans.append(f'The number of articles from the section {si.index} in this record: {num}')
-                        ' in this record: %s'%(si.index, num))
             elif 0b0001 in extra:
                 eof = extra[0b0001]
                 if eof != 0:
@@ -791,7 +772,7 @@ class MOBIFile:  # {{{
         p()
         p('Record headers:')
         for i, r in enumerate(self.records):
-            p('%6d. %s'%(i, r.header))
+            p(f'{i:6}. {r.header}')
 
         p()
         p(str(self.mobi_header))

src/calibre/ebooks/mobi/debug/mobi8.py

@@ -53,7 +53,7 @@ class FDST:
 class File:
 
     def __init__(self, skel, skeleton, text, first_aid, sections):
-        self.name = 'part%04d'%skel.file_number
+        self.name = f'part{skel.file_number:04}'
         self.skeleton, self.text, self.first_aid = skeleton, text, first_aid
         self.sections = sections
 
@@ -66,7 +66,7 @@ class File:
             with open('skeleton.html', 'wb') as f:
                 f.write(self.skeleton)
             for i, text in enumerate(self.sections):
-                with open('sect-%04d.html'%i, 'wb') as f:
+                with open(f'sect-{i:04}.html', 'wb') as f:
                     f.write(text)
 
 
@@ -101,7 +101,7 @@ class MOBIFile:
         p()
         p('Record headers:')
         for i, r in enumerate(self.mf.records):
-            p('%6d. %s'%(i, r.header))
+            p(f'{i:6}. {r.header}')
 
         p()
         p(str(self.mf.mobi8_header))
@@ -151,7 +151,7 @@ class MOBIFile:
         for i, x in enumerate(boundaries):
             start, end = x
             raw = self.raw_text[start:end]
-            with open(os.path.join(ddir, 'flow%04d.txt'%i), 'wb') as f:
+            with open(os.path.join(ddir, f'flow{i:04}.txt'), 'wb') as f:
                 f.write(raw)
 
     def extract_resources(self, records):
@@ -221,7 +221,7 @@ class MOBIFile:
                 elif sig in known_types:
                     suffix = '-' + sig.decode('ascii')
 
-            self.resource_map.append(('%s/%06d%s.%s'%(prefix, resource_index, suffix, ext),
+            self.resource_map.append((f'{prefix}/{resource_index:06}{suffix}.{ext}',
                 payload))
 
     def read_tbs(self):
@@ -260,9 +260,9 @@ class MOBIFile:
         for i, strands in enumerate(indexing_data):
             rec = self.text_records[i]
             tbs_bytes = rec.trailing_data.get('indexing', b'')
-            desc = ['Record #%d'%i]
+            desc = [f'Record #{i}']
             for s, strand in enumerate(strands):
-                desc.append('Strand %d'%s)
+                desc.append(f'Strand {s}')
                 for entries in itervalues(strand):
                     for e in entries:
                         desc.append(
@@ -284,7 +284,7 @@ class MOBIFile:
                 extra = {bin(k):v for k, v in iteritems(extra)}
                 sequences.append((val, extra))
             for j, seq in enumerate(sequences):
-                desc.append('Sequence #%d: %r %r'%(j, seq[0], seq[1]))
+                desc.append(f'Sequence #{j}: {seq[0]!r} {seq[1]!r}')
             if tbs_bytes:
                 desc.append(f'Remaining bytes: {format_bytes(tbs_bytes)}')
             calculated_sequences = encode_strands_as_sequences(strands,
@@ -294,7 +294,7 @@ class MOBIFile:
             except:
                 calculated_bytes = b'failed to calculate tbs bytes'
             if calculated_bytes != otbs:
-                print('WARNING: TBS mismatch for record %d'%i)
+                print(f'WARNING: TBS mismatch for record {i}')
                 desc.append('WARNING: TBS mismatch!')
                 desc.append(f'Calculated sequences: {calculated_sequences!r}')
             desc.append('')
@@ -321,7 +321,7 @@ def inspect_mobi(mobi_file, ddir):
             fo.write(payload)
 
     for i, container in enumerate(f.containers):
-        with open(os.path.join(ddir, 'container%d.txt' % (i + 1)), 'wb') as cf:
+        with open(os.path.join(ddir, f'container{i + 1}.txt'), 'wb') as cf:
             cf.write(str(container).encode('utf-8'))
 
     if f.fdst:

src/calibre/ebooks/mobi/reader/headers.py

@@ -220,8 +220,7 @@ class BookHeader:
                     }[self.codepage]
             except (IndexError, KeyError):
                 self.codec = 'cp1252' if not user_encoding else user_encoding
-                log.warn('Unknown codepage %d. Assuming %s' % (self.codepage,
+                log.warn(f'Unknown codepage {self.codepage}. Assuming {self.codec}')
-                    self.codec))
             # Some KF8 files have header length == 264 (generated by kindlegen
             # 2.9?). See https://bugs.launchpad.net/bugs/1179144
             max_header_length = 500  # We choose 500 for future versions of kindlegen

src/calibre/ebooks/mobi/reader/index.py

@@ -16,7 +16,7 @@ PTagX = namedtuple('PTagX', 'tag value_count value_bytes num_of_values')
 INDEX_HEADER_FIELDS = (
             'len', 'nul1', 'type', 'gen', 'start', 'count', 'code',
             'lng', 'total', 'ordt', 'ligt', 'nligt', 'ncncx'
-    ) + tuple('unknown%d'%i for i in range(27)) + ('ocnt', 'oentries',
+    ) + tuple(f'unknown{i}' for i in range(27)) + ('ocnt', 'oentries',
             'ordt1', 'ordt2', 'tagx')
 
 
@@ -47,7 +47,7 @@ def parse_indx_header(data):
     check_signature(data, b'INDX')
     words = INDEX_HEADER_FIELDS
     num = len(words)
-    values = struct.unpack('>%dL' % num, data[4:4*(num+1)])
+    values = struct.unpack(f'>{num}L', data[4:4*(num+1)])
     ans = dict(zip(words, values))
     ans['idx_header_end_pos'] = 4 * (num+1)
     ordt1, ordt2 = ans['ordt1'], ans['ordt2']
@@ -103,8 +103,7 @@ class CNCX:  # {{{
                     except:
                         byts = raw[pos:]
                         r = format_bytes(byts)
-                        print('CNCX entry at offset %d has unknown format %s'%(
+                        print(f'CNCX entry at offset {pos + record_offset} has unknown format {r}')
-                            pos+record_offset, r))
                         self.records[pos+record_offset] = r
                         pos = len(raw)
                 pos += consumed+length

src/calibre/ebooks/mobi/reader/mobi6.py

@@ -525,7 +525,7 @@ class MobiReader:
                     except Exception:
                         pass
                     else:
-                        attrib['src'] = 'images/' + image_name_map.get(recindex, '%05d.jpg' % recindex)
+                        attrib['src'] = 'images/' + image_name_map.get(recindex, f'{recindex:05}.jpg')
                 for attr in ('width', 'height'):
                     if attr in attrib:
                         val = attrib[attr]
@@ -577,7 +577,7 @@ class MobiReader:
                         ncls = sel
                         break
                 if ncls is None:
-                    ncls = 'calibre_%d' % i
+                    ncls = f'calibre_{i}'
                     self.tag_css_rules[ncls] = rule
                 cls = attrib.get('class', '')
                 cls = cls + (' ' if cls else '') + ncls
@@ -658,7 +658,7 @@ class MobiReader:
             mi = MetaInformation(self.book_header.title, [_('Unknown')])
         opf = OPFCreator(os.path.dirname(htmlfile), mi)
         if hasattr(self.book_header.exth, 'cover_offset'):
-            opf.cover = 'images/%05d.jpg' % (self.book_header.exth.cover_offset + 1)
+            opf.cover = f'images/{self.book_header.exth.cover_offset + 1:05}.jpg'
         elif mi.cover is not None:
             opf.cover = mi.cover
         else:
@@ -920,7 +920,7 @@ class MobiReader:
                 except OSError:
                     self.log.warn(f'Ignoring undecodeable GIF image at index {image_index}')
                     continue
-            path = os.path.join(output_dir, '%05d.%s' % (image_index, imgfmt))
+            path = os.path.join(output_dir, f'{image_index:05}.{imgfmt}')
             image_name_map[image_index] = os.path.basename(path)
             if imgfmt == 'png':
                 with open(path, 'wb') as f:

src/calibre/ebooks/mobi/reader/mobi8.py

@@ -200,7 +200,7 @@ class Mobi8Reader:
                                     self.elems[divptr]
                 if i == 0:
                     aidtext = idtext[12:-2]
-                    filename = 'part%04d.html' % filenum
+                    filename = f'part{filenum:04}.html'
                 part = text[baseptr:baseptr + length]
                 insertpos = insertpos - skelpos
                 head = skeleton[:insertpos]
@@ -256,7 +256,7 @@ class Mobi8Reader:
         image_tag_pattern = re.compile(br'''(<(?:svg:)?image[^>]*>)''', re.IGNORECASE)
         for j in range(1, len(self.flows)):
             flowpart = self.flows[j]
-            nstr = '%04d' % j
+            nstr = f'{j:04}'
             m = svg_tag_pattern.search(flowpart)
             if m is not None:
                 # svg
@@ -320,7 +320,7 @@ class Mobi8Reader:
         # pos
         fi = self.get_file_info(pos)
         if fi.num is None and fi.start is None:
-            raise ValueError('No file contains pos: %d'%pos)
+            raise ValueError(f'No file contains pos: {pos}')
         textblock = self.parts[fi.num]
         npos = pos - fi.start
         pgt = textblock.find(b'>', npos)
@@ -391,7 +391,7 @@ class Mobi8Reader:
                 pos = entry['pos']
                 fi = self.get_file_info(pos)
                 if fi.filename is None:
-                    raise ValueError('Index entry has invalid pos: %d'%pos)
+                    raise ValueError(f'Index entry has invalid pos: {pos}')
                 idtag = self.get_id_tag(pos)
                 href = f'{fi.type}/{fi.filename}'
             else:
@@ -429,10 +429,9 @@ class Mobi8Reader:
                     pass  # Ignore these records
                 elif typ == b'FONT':
                     font = read_font_record(data)
-                    href = 'fonts/%05d.%s' % (fname_idx, font['ext'])
+                    href = f"fonts/{fname_idx:05}.{font['ext']}"
                     if font['err']:
-                        self.log.warn('Reading font record %d failed: %s'%(
+                        self.log.warn(f"Reading font record {fname_idx} failed: {font['err']}")
-                            fname_idx, font['err']))
                         if font['headers']:
                             self.log.debug('Font record headers: {}'.format(font['headers']))
                     with open(href.replace('/', os.sep), 'wb') as f:
@@ -448,7 +447,7 @@ class Mobi8Reader:
                 elif typ == b'CRES':
                     data, imgtype = container.load_image(data)
                     if data is not None:
-                        href = 'images/%05d.%s'%(container.resource_index, imgtype)
+                        href = f'images/{container.resource_index:05}.{imgtype}'
                         with open(href.replace('/', os.sep), 'wb') as f:
                             f.write(data)
                 elif typ == b'\xa0\xa0\xa0\xa0' and len(data) == 4 and container is not None:
@@ -456,7 +455,7 @@ class Mobi8Reader:
                 elif container is None:
                     if not (len(data) == len(PLACEHOLDER_GIF) and data == PLACEHOLDER_GIF):
                         imgtype = find_imgtype(data)
-                        href = 'images/%05d.%s'%(fname_idx, imgtype)
+                        href = f'images/{fname_idx:05}.{imgtype}'
                         with open(href.replace('/', os.sep), 'wb') as f:
                             f.write(data)
 

src/calibre/ebooks/mobi/utils.py

@@ -156,8 +156,7 @@ def test_decint(num):
         raw = encint(num, forward=d)
         sz = len(raw)
         if (num, sz) != decint(raw, forward=d):
-            raise ValueError('Failed for num %d, forward=%r: %r != %r' % (
+            raise ValueError(f'Failed for num {num}, forward={d!r}: {num, sz!r} != {decint(raw, forward=d)!r}')
-                num, d, (num, sz), decint(raw, forward=d)))
 
 
 def rescale_image(data, maxsizeb=IMAGE_MAX_SIZE, dimen=None):

src/calibre/ebooks/mobi/writer2/serializer.py

@@ -390,4 +390,4 @@ class Serializer:
                     self.start_offset = ioff
                 for hoff in hoffs:
                     buf.seek(hoff)
-                    buf.write(('%010d' % ioff).encode('utf-8'))
+                    buf.write(f'{ioff:010}'.encode('utf-8'))

src/calibre/ebooks/mobi/writer8/index.py

@@ -267,7 +267,7 @@ class ChunkIndex(Index):
         self.cncx = CNCX(c.selector for c in chunk_table)
 
         self.entries = [
-                ('%010d'%c.insert_pos, {
+                (f'{c.insert_pos:010}', {
 
                     'cncx_offset':self.cncx[c.selector],
                     'file_number':c.file_number,
@@ -378,7 +378,7 @@ if __name__ == '__main__':
     import os
     import subprocess
     os.chdir('/t')
-    paras = ['<p>%d</p>' % i for i in range(4000)]
+    paras = [f'<p>{i}</p>' for i in range(4000)]
     raw = '<html><body>' + '\n\n'.join(paras) + '</body></html>'
 
     src = 'index.html'

src/calibre/ebooks/mobi/writer8/main.py

@@ -302,7 +302,7 @@ class KF8Writer:
                         # https://bugs.launchpad.net/bugs/1489495
                         if id_:
                             cid += 1
-                            val = 'c%d' % cid
+                            val = f'c{cid}'
                             self.id_map[(item.href, id_)] = val
                             tag.set('cid', val)
                     else:

src/calibre/ebooks/mobi/writer8/skeleton.py

@@ -341,7 +341,7 @@ class Chunker:
         for s in self.skeletons:
             s.start_pos = sp
             sp += len(s)
-        self.skel_table = [Skel(s.file_number, 'SKEL%010d'%s.file_number,
+        self.skel_table = [Skel(s.file_number, f'SKEL{s.file_number:010}',
             len(s.chunks), s.start_pos, len(s.skeleton)) for s in self.skeletons]
 
         Chunk = namedtuple('Chunk',
@@ -426,13 +426,13 @@ class Chunker:
         error = False
         for i, skeleton in enumerate(self.skeletons):
             for j, chunk in enumerate(skeleton.chunks):
-                with open(os.path.join(chunks, 'file-%d-chunk-%d.html'%(i, j)),
+                with open(os.path.join(chunks, f'file-{i}-chunk-{j}.html'),
                         'wb') as f:
                     f.write(chunk.raw)
             oraw, rraw = orig_dumps[i], skeleton.rebuild()
-            with open(os.path.join(orig, '%04d.html'%i), 'wb') as f:
+            with open(os.path.join(orig, f'{i:04}.html'), 'wb') as f:
                 f.write(oraw)
-            with open(os.path.join(rebuilt, '%04d.html'%i), 'wb') as f:
+            with open(os.path.join(rebuilt, f'{i:04}.html'), 'wb') as f:
                 f.write(rraw)
             if oraw != rraw:
                 error = True

src/calibre/ebooks/odt/input.py

@@ -200,7 +200,7 @@ class Extract(ODF2XHTML):
                 # Replace all the class selectors with a single class selector
                 # This will be added to the class attribute of all elements
                 # that have one of these selectors.
-                replace_name = 'c_odt%d'%count
+                replace_name = f'c_odt{count}'
                 count += 1
                 for sel in r.selectorList:
                     s = sel.selectorText[1:]

src/calibre/ebooks/oeb/iterator/bookmarks.py

@@ -57,7 +57,7 @@ class BookmarksMixin:
         dat = []
         for bm in bookmarks:
             if bm['type'] == 'legacy':
-                rec = '%s^%d#%s'%(bm['title'], bm['spine'], bm['pos'])
+                rec = f"{bm['title']}^{bm['spine']}#{bm['pos']}"
             else:
                 pos = bm['pos']
                 if isinstance(pos, numbers.Number):

src/calibre/ebooks/oeb/parse_utils.py

@@ -103,8 +103,7 @@ def html5_parse(data, max_nesting_depth=100):
         if isinstance(x.tag, string_or_bytes) and not len(x):  # Leaf node
             depth = node_depth(x)
             if depth > max_nesting_depth:
-                raise ValueError('HTML 5 parsing resulted in a tree with nesting'
+                raise ValueError(f'HTML 5 parsing resulted in a tree with nesting depth > {max_nesting_depth}')
-                        ' depth > %d'%max_nesting_depth)
     return data
 
 

src/calibre/ebooks/oeb/polish/check/links.py

@@ -231,7 +231,7 @@ class MimetypeMismatch(BaseError):
             c = 0
             while container.has_name(new_name):
                 c += 1
-                new_name = self.file_name.rpartition('.')[0] + ('%d.' % c) + self.change_ext_to
+                new_name = self.file_name.rpartition('.')[0] + f'{c}.' + self.change_ext_to
             rename_files(container, {self.file_name:new_name})
             changed = True
         else:

src/calibre/ebooks/oeb/polish/check/parsing.py

@@ -146,7 +146,7 @@ class EscapedName(BaseError):
         c = 0
         while self.sname in all_names:
             c += 1
-            self.sname = '%s_%d.%s' % (bn, c, ext)
+            self.sname = f'{bn}_{c}.{ext}'
         rename_files(container, {self.name:self.sname})
         return True
 

src/calibre/ebooks/oeb/polish/container.py

@@ -344,7 +344,7 @@ class Container(ContainerBase):  # {{{
         item_id = 'id'
         while item_id in all_ids:
             c += 1
-            item_id = 'id' + '%d'%c
+            item_id = 'id' + f'{c}'
         manifest = self.opf_xpath('//opf:manifest')[0]
         href = self.name_to_href(name, self.opf_name)
         item = manifest.makeelement(OPF('item'),
@@ -369,7 +369,7 @@ class Container(ContainerBase):  # {{{
             base, ext = name.rpartition('.')[::2]
             if c > 1:
                 base = base.rpartition('-')[0]
-            name = '%s-%d.%s' % (base, c, ext)
+            name = f'{base}-{c}.{ext}'
         return name
 
     def add_file(self, name, data, media_type=None, spine_index=None, modify_name_if_needed=False, process_manifest_item=None):

src/calibre/ebooks/oeb/polish/cover.py

@@ -382,7 +382,7 @@ def create_epub_cover(container, cover_path, existing_image, options=None):
                 container.log.exception('Failed to get width and height of cover')
             ar = 'xMidYMid meet' if keep_aspect else 'none'
             templ = CoverManager.SVG_TEMPLATE.replace('__ar__', ar)
-            templ = templ.replace('__viewbox__', '0 0 %d %d'%(width, height))
+            templ = templ.replace('__viewbox__', f'0 0 {width} {height}')
             templ = templ.replace('__width__', str(width))
             templ = templ.replace('__height__', str(height))
     folder = recommended_folders[tname]

src/calibre/ebooks/oeb/polish/images.py

@@ -98,7 +98,7 @@ def compress_images(container, report=None, names=None, jpeg_quality=None, webp_
         if not keep_going:
             abort.set()
     progress_callback(0, num_to_process, '')
-    [Worker(abort, 'CompressImage%d' % i, queue, results, jpeg_quality, webp_quality, pc) for i in range(min(detect_ncpus(), num_to_process))]
+    [Worker(abort, f'CompressImage{i}', queue, results, jpeg_quality, webp_quality, pc) for i in range(min(detect_ncpus(), num_to_process))]
     queue.join()
     before_total = after_total = 0
     processed_num = 0

src/calibre/ebooks/oeb/polish/replace.py

@@ -218,7 +218,7 @@ def replace_file(container, name, path, basename, force_mt=None):
             b, e = nname.rpartition('.')[0::2]
             while container.exists(nname):
                 count += 1
-                nname = b + ('_%d.%s' % (count, e))
+                nname = b + f'_{count}.{e}'
             rename_files(container, {name:nname})
             mt = force_mt or container.guess_type(nname)
             container.mime_map[nname] = mt
@@ -308,7 +308,7 @@ def rationalize_folders(container, folder_type_map):
                 while new_name in all_names or new_name in new_names:
                     c += 1
                     n, ext = bn.rpartition('.')[0::2]
-                    new_name = posixpath.join(folder, '%s_%d.%s' % (n, c, ext))
+                    new_name = posixpath.join(folder, f'{n}_{c}.{ext}')
                 name_map[name] = new_name
                 new_names.add(new_name)
     return name_map

src/calibre/ebooks/oeb/polish/split.py

@@ -215,7 +215,7 @@ def split(container, name, loc_or_xpath, before=True, totals=None):
     nname, s = None, 0
     while not nname or container.exists(nname):
         s += 1
-        nname = '%s_split%d.%s' % (base, s, ext)
+        nname = f'{base}_split{s}.{ext}'
     manifest_item = container.generate_item(nname, media_type=container.mime_map[name])
     bottom_name = container.href_to_name(manifest_item.get('href'), container.opf_name)
 
@@ -287,7 +287,7 @@ def multisplit(container, name, xpath, before=True):
     current = name
     all_names = [name]
     for i in range(len(nodes)):
-        current = split(container, current, '//*[@calibre-split-point="%d"]' % i, before=before)
+        current = split(container, current, f'//*[@calibre-split-point="{i}"]', before=before)
         all_names.append(current)
 
     for x in all_names:
@@ -345,7 +345,7 @@ def unique_anchor(seen_anchors, current):
     ans = current
     while ans in seen_anchors:
         c += 1
-        ans = '%s_%d' % (current, c)
+        ans = f'{current}_{c}'
     return ans
 
 

src/calibre/ebooks/oeb/polish/tests/structure.py

@@ -51,7 +51,7 @@ def create_epub(manifest, spine=(), guide=(), meta_cover=None, ver=3):
         spine = [x[0] for x in manifest if guess_type(x[0]) in OEB_DOCS]
     spine = ''.join(f'<itemref idref="{name}"/>' for name in spine)
     guide = ''.join(f'<reference href="{name}" type="{typ}" title="{title}"/>' for name, typ, title in guide)
-    opf = OPF_TEMPLATE.format(manifest=mo, ver='%d.0'%ver, metadata=metadata, spine=spine, guide=guide)
+    opf = OPF_TEMPLATE.format(manifest=mo, ver=f'{ver}.0', metadata=metadata, spine=spine, guide=guide)
     buf = BytesIO()
     with ZipFile(buf, 'w', ZIP_STORED) as zf:
         zf.writestr('META-INF/container.xml', b'''
@@ -79,7 +79,7 @@ class Structure(BaseTest):
         ep = os.path.join(self.tdir, str(n) + 'book.epub')
         with open(ep, 'wb') as f:
             f.write(create_epub(*args, **kw).getvalue())
-        c = get_container(ep, tdir=os.path.join(self.tdir, 'container%d' % n), tweak_mode=True)
+        c = get_container(ep, tdir=os.path.join(self.tdir, f'container{n}'), tweak_mode=True)
         return c
 
     def test_toc_detection(self):

src/calibre/ebooks/oeb/polish/toc.py

@@ -622,7 +622,7 @@ def create_ncx(toc, to_href, btitle, lang, uid):
     def process_node(xml_parent, toc_parent):
         for child in toc_parent:
             play_order['c'] += 1
-            point = etree.SubElement(xml_parent, NCX('navPoint'), id='num_%d' % play_order['c'],
+            point = etree.SubElement(xml_parent, NCX('navPoint'), id=f"num_{play_order['c']}",
                             playOrder=str(play_order['c']))
             label = etree.SubElement(point, NCX('navLabel'))
             title = child.title
@@ -853,7 +853,7 @@ def toc_to_html(toc, container, toc_name, title, lang=None):
         li.append(a)
         if len(toc) > 0:
             parent = li.makeelement(XHTML('ul'))
-            parent.set('class', 'level%d' % (style_level))
+            parent.set('class', f'level{style_level}')
             li.append(parent)
             a.tail = '\n\n' + (indent*(level+2))
             parent.text = '\n'+(indent*(level+3))
@@ -909,7 +909,7 @@ def create_inline_toc(container, title=None):
         name, c = 'toc.xhtml', 0
         while container.has_name(name):
             c += 1
-            name = 'toc%d.xhtml' % c
+            name = f'toc{c}.xhtml'
         container.add_file(name, raw, spine_index=0)
     else:
         with container.open(name, 'wb') as f:

src/calibre/ebooks/oeb/transforms/cover.py

@@ -142,7 +142,7 @@ class CoverManager:
             # if self.preserve_aspect_ratio:
             #     width, height = 600, 800
             self.svg_template = self.svg_template.replace('__viewbox__',
-                    '0 0 %d %d'%(width, height))
+                    f'0 0 {width} {height}')
             self.svg_template = self.svg_template.replace('__width__',
                     str(width))
             self.svg_template = self.svg_template.replace('__height__',

src/calibre/ebooks/oeb/transforms/filenames.py

@@ -132,7 +132,7 @@ class UniqueFilenames:  # {{{
         c = 0
         while True:
             c += 1
-            suffix = '_u%d'%c
+            suffix = f'_u{c}'
             candidate = base + suffix + ext
             if candidate not in self.seen_filenames:
                 return suffix

src/calibre/ebooks/oeb/transforms/page_margin.py

@@ -143,7 +143,7 @@ class RemoveFakeMargins:
 
             for p in paras(body):
                 level = level_of(p, body)
-                level = '%s_%d'%(barename(p.tag), level)
+                level = f'{barename(p.tag)}_{level}'
                 if level not in self.levels:
                     self.levels[level] = []
                 self.levels[level].append(p)
@@ -151,7 +151,7 @@ class RemoveFakeMargins:
         remove = set()
         for k, v in iteritems(self.levels):
             num = len(v)
-            self.log.debug('Found %d items of level:'%num, k)
+            self.log.debug(f'Found {num} items of level:', k)
             level = int(k.split('_')[-1])
             tag = k.split('_')[0]
             if tag == 'p' and num < 25:

src/calibre/ebooks/oeb/transforms/rasterize.py

@@ -217,8 +217,7 @@ class SVGRasterizer:
             href = self.images[key]
         else:
             logger = self.oeb.logger
-            logger.info('Rasterizing %r to %dx%d'
+            logger.info(f'Rasterizing {svgitem.href!r} to {size.width()}x{size.height()}')
-                        % (svgitem.href, size.width(), size.height()))
             image = QImage(size, QImage.Format.Format_ARGB32_Premultiplied)
             image.fill(QColor('white').rgb())
             painter = QPainter(image)