diff --git a/src/calibre/devices/kobo/driver.py b/src/calibre/devices/kobo/driver.py
index 3d0a403429..3b9c56e15c 100644
--- a/src/calibre/devices/kobo/driver.py
+++ b/src/calibre/devices/kobo/driver.py
@@ -1742,7 +1742,8 @@ class KOBOTOUCH(KOBO):
             if show_debug:
                 debug_print(f"KoboTouch:update_booklist - title='{title}'", f'ContentType={ContentType}', 'isdownloaded=', isdownloaded)
                 debug_print(
-                    f'         prefix={prefix}, DateCreated={DateCreated}, readstatus={readstatus}, MimeType={MimeType}, expired={expired}, favouritesindex={favouritesindex}, accessibility={accessibility}, isdownloaded={isdownloaded}')
+                    f'         prefix={prefix}, DateCreated={DateCreated}, readstatus={readstatus}, MimeType={MimeType},'
+                    f' expired={expired}, favouritesindex={favouritesindex}, accessibility={accessibility}, isdownloaded={isdownloaded}')
             changed = False
             try:
                 lpath = path.partition(self.normalize_path(prefix))[2]
@@ -2720,7 +2721,8 @@ class KOBOTOUCH(KOBO):
                     debug_print('KoboTouch:update_device_database_collections - about to clear empty bookshelves')
                     self.delete_empty_bookshelves(connection)
                 debug_print(f'KoboTouch:update_device_database_collections - Number of series set={self.series_set} Number of books={books_in_library}')
-                debug_print(f'KoboTouch:update_device_database_collections - Number of core metadata set={self.core_metadata_set} Number of books={books_in_library}')
+                debug_print(f'KoboTouch:update_device_database_collections - Number of core metadata set={self.core_metadata_set}'
+                            f' Number of books={books_in_library}')
 
                 self.dump_bookshelves(connection)
 
@@ -2914,7 +2916,8 @@ 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(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}')
+                        debug_print(f'KoboTouch:_upload_cover - library_cover_size={library_cover_size} -> kobo_size={kobo_size},'
+                                    f' min_dbversion={min_dbversion} max_dbversion={max_dbversion}, is_full_size={is_full_size}')
 
                     if self.dbversion >= min_dbversion and self.dbversion <= max_dbversion:
                         if show_debug:
diff --git a/src/calibre/devices/winusb.py b/src/calibre/devices/winusb.py
index 7b70938fc9..b183aae199 100644
--- a/src/calibre/devices/winusb.py
+++ b/src/calibre/devices/winusb.py
@@ -179,7 +179,10 @@ class USB_DEVICE_DESCRIPTOR(Structure):
     )
 
     def __repr__(self):
-        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})'
+        return (
+            f'USBDevice(class=0x{self.bDeviceClass:x} sub_class=0x{self.bDeviceSubClass:x} protocol=0x{self.bDeviceProtocol:x}'
+            f' vendor_id=0x{self.idVendor:x} product_id=0x{self.idProduct:x} bcd=0x{self.bcdDevice:x} manufacturer={self.iManufacturer}'
+            f'product={self.iProduct} serial_number={self.iSerialNumber})')
 
 
 class USB_ENDPOINT_DESCRIPTOR(Structure):
diff --git a/src/calibre/ebooks/lit/reader.py b/src/calibre/ebooks/lit/reader.py
index 4af6a3b118..f6df491afd 100644
--- a/src/calibre/ebooks/lit/reader.py
+++ b/src/calibre/ebooks/lit/reader.py
@@ -396,7 +396,7 @@ class DirectoryEntry:
         self.size = size
 
     def __repr__(self):
-        return f'DirectoryEntry(name={repr(self.name)}, section={self.section}, offset={self.offset}, size={self.size})'
+        return f'DirectoryEntry(name={self.name!r}, section={self.section}, offset={self.offset}, size={self.size})'
 
     def __str__(self):
         return repr(self)
@@ -427,7 +427,9 @@ class ManifestItem:
         return self.internal == other
 
     def __repr__(self):
-        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})"
+        return (
+            f'ManifestItem(internal={self.internal!r}, path={self.path!r}, mime_type={self.mime_type!r},'
+            f' offset={self.offset}, root={self.root!r}, state={self.state!r})')
 
 
 def preserve(function):
diff --git a/src/calibre/ebooks/lrf/objects.py b/src/calibre/ebooks/lrf/objects.py
index 485f5a9bc4..dc2994aec8 100644
--- a/src/calibre/ebooks/lrf/objects.py
+++ b/src/calibre/ebooks/lrf/objects.py
@@ -932,7 +932,9 @@ class Image(LRFObject):
     data = property(fget=lambda self: self._document.objects[self.refstream].stream)
 
     def __str__(self):
-        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'
+        return (
+            f'<Image objid="{self.id}" x0="{self.x0}" y0="{self.y0}" x1="{self.x1}" y1="{self.y1}"'
+            f' xsize="{self.xsize}" ysize="{self.ysize}" refstream="{self.refstream}" />\n')
 
 
 class PutObj(EmptyPageElement):
diff --git a/src/calibre/ebooks/mobi/debug/mobi6.py b/src/calibre/ebooks/mobi/debug/mobi6.py
index 3abe56b3e7..99a55f6555 100644
--- a/src/calibre/ebooks/mobi/debug/mobi6.py
+++ b/src/calibre/ebooks/mobi/debug/mobi6.py
@@ -591,7 +591,7 @@ class TBSIndexing:  # {{{
             if entries:
                 ans.append(f'\t{typ}:')
                 for x in entries:
-                    ans.append(f"\t\tIndex Entry: {x.index} (Parent index: {x.parent_index}, Depth: {x.depth}, Offset: {x.offset}, Size: {x.size}) [{x.label}]")
+                    ans.append(f'\t\tIndex Entry: {x.index} (Parent index: {x.parent_index}, Depth: {x.depth}, Offset: {x.offset}, Size: {x.size}) [{x.label}]')
 
         def bin4(num):
             ans = bin(num)[2:]
@@ -646,7 +646,9 @@ 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(f'Last article in this record of section {psi.index} (relative to next section index [{nsi.index}]): {ai} [{ai + nsi.index} absolute index]')
+                    ans.append(
+                        f'Last article in this record of section {psi.index} (relative to next section index [{nsi.index}]):'
+                        f' {ai} [{ai + nsi.index} absolute index]')
                     psi = nsi
                     continue
 
@@ -654,9 +656,9 @@ class TBSIndexing:  # {{{
 
                 num = extra.get(0b0100, None)
                 if num is None:
-                    msg = f"The section {psi.index} has at most one article in this record"
+                    msg = f'The section {psi.index} has at most one article in this record'
                 else:
-                    msg = f"Number of articles in this record of section {psi.index}: {num}"
+                    msg = f'Number of articles in this record of section {psi.index}: {num}'
                 ans.append(msg)
 
                 offset = extra.get(0b0001, None)
@@ -664,7 +666,9 @@ class TBSIndexing:  # {{{
                     if offset == 0:
                         ans.append(f'This record is spanned by the article:{ai + psi.index}')
                     else:
-                        ans.append(f'->Offset to start of next section ({psi.index + 1}) from start of record: {offset} [{offset + record_offset} absolute offset]')
+                        ans.append(
+                            f'->Offset to start of next section ({psi.index + 1}) from start of record:'
+                            f' {offset} [{offset + record_offset} absolute offset]')
             return byts
         # }}}
 
diff --git a/src/calibre/ebooks/pdb/ztxt/reader.py b/src/calibre/ebooks/pdb/ztxt/reader.py
index 54141c6901..ce51ce19fd 100644
--- a/src/calibre/ebooks/pdb/ztxt/reader.py
+++ b/src/calibre/ebooks/pdb/ztxt/reader.py
@@ -48,7 +48,8 @@ class Reader(FormatReader):
         vmajor = (self.header_record.version & 0x0000FF00) >> 8
         vminor = self.header_record.version & 0x000000FF
         if vmajor < 1 or (vmajor == 1 and vminor < 40):
-            raise zTXTError(f'Unsupported ztxt version ({vmajor}.{vminor}). Only versions newer than {SUPPORTED_VERSION[0]}.{SUPPORTED_VERSION[1]} are supported.')
+            raise zTXTError(f'Unsupported ztxt version ({vmajor}.{vminor}).'
+                            f' Only versions newer than {SUPPORTED_VERSION[0]}.{SUPPORTED_VERSION[1]} are supported.')
 
         if (self.header_record.flags & 0x01) == 0:
             raise zTXTError('Only compression method 1 (random access) is supported')
diff --git a/src/calibre/ebooks/pdf/reflow.py b/src/calibre/ebooks/pdf/reflow.py
index abcf8a7883..f4a916141f 100644
--- a/src/calibre/ebooks/pdf/reflow.py
+++ b/src/calibre/ebooks/pdf/reflow.py
@@ -271,8 +271,8 @@ class Text(Element):
         if self.font_size_em == other.font_size_em \
           and False \
           and self.font.id == other.font.id \
-          and re.match(r'<span style="font-size:', self.raw) is not None \
-          and re.match(r'<span style="font-size:', other.raw) is not None:
+          and self.raw.startswith(r'<span style="font-size:') \
+          and other.raw.startswith(r'<span style="font-size:'):
             # We have the same class, so merge
             m_self = re.match(r'^(.+)</span>$', self.raw)
             m_other = re.match(r'^<span style="font-size:.+em">(.+</span>)$', other.raw)
@@ -281,7 +281,7 @@ class Text(Element):
                 other.raw = m_other.group(1)
         elif self.font_size_em != other.font_size_em \
           and self.font_size_em != 1.00:
-            if re.match(r'<span', self.raw) is None:
+            if not self.raw.startswith(r'<span'):
                 self.raw = f'<span style="font-size:{self.font_size_em!s}em">{self.raw}</span>'
             # Try to allow for a very large initial character
             elif len(self.text_as_string) <= 2 \
diff --git a/src/calibre/gui2/tweak_book/editor/snippets.py b/src/calibre/gui2/tweak_book/editor/snippets.py
index 8a91389c7b..6ef59672ea 100644
--- a/src/calibre/gui2/tweak_book/editor/snippets.py
+++ b/src/calibre/gui2/tweak_book/editor/snippets.py
@@ -159,7 +159,9 @@ class TabStop(str):
         return self
 
     def __repr__(self):
-        return f'TabStop(text={str.__repr__(self)} num={self.num} start={self.start} is_mirror={self.is_mirror} takes_selection={self.takes_selection} is_toplevel={self.is_toplevel})'
+        return (
+            f'TabStop(text={str.__repr__(self)} num={self.num} start={self.start} is_mirror={self.is_mirror}'
+            f' takes_selection={self.takes_selection} is_toplevel={self.is_toplevel})')
 
 
 def parse_template(template, start_offset=0, is_toplevel=True, grouped=True):
diff --git a/src/calibre/gui2/update.py b/src/calibre/gui2/update.py
index a34c82520e..eaf4be710a 100644
--- a/src/calibre/gui2/update.py
+++ b/src/calibre/gui2/update.py
@@ -219,7 +219,7 @@ class UpdateMixin:
                             green, _('Update available'), version_url, calibre_version, plt)
         else:
             plt = ngettext('plugin update available', 'plugin updates available', number_of_plugin_updates)
-            msg = f"<a href=\"update:{version_url}\">{number_of_plugin_updates} {plt}</a>"
+            msg = f'<a href="update:{version_url}">{number_of_plugin_updates} {plt}</a>'
         self.status_bar.update_label.setText(msg)
         self.status_bar.update_label.setVisible(True)
 
diff --git a/src/calibre/utils/exim.py b/src/calibre/utils/exim.py
index b28cfcee9f..92e8be0a56 100644
--- a/src/calibre/utils/exim.py
+++ b/src/calibre/utils/exim.py
@@ -377,7 +377,8 @@ class Importer:
                     raise ValueError(f'The exported data in {name} is not valid, tail too small')
                 part_num, version, is_last = struct.unpack(Exporter.TAIL_FMT, raw)
                 if version > Exporter.VERSION:
-                    raise ValueError(f'The exported data in {name} is not valid, version ({version}) is higher than maximum supported version. You might need to upgrade calibre first.')
+                    raise ValueError(f'The exported data in {name} is not valid, version ({version})'
+                                     ' is higher than maximum supported version. You might need to upgrade calibre first.')
                 part_map[part_num] = path, is_last, size_of_part
                 if self.version == -1:
                     self.version = version
diff --git a/src/calibre/utils/mem.py b/src/calibre/utils/mem.py
index 72d0acc9ad..3687eb1d7b 100644
--- a/src/calibre/utils/mem.py
+++ b/src/calibre/utils/mem.py
@@ -47,4 +47,4 @@ def diff_hists(h1, h2):
         if k not in h2:
             h2[k] = 0
         if h1[k] != h2[k]:
-            print(f"{k}: {h1[k]} -> {h2[k]} ({h2[k] > h1[k] and '+' or ''}{h2[k] - h1[k]})")
+            print(f"{k}: {h1[k]} -> {h2[k]} ({(h2[k] > h1[k] and '+') or ''}{h2[k] - h1[k]})")