diff --git a/setup/build.py b/setup/build.py
index 8282960ab2..4e105cb6e6 100644
--- a/setup/build.py
+++ b/setup/build.py
@@ -441,7 +441,7 @@ class Build(Command):
             os.makedirs(x, exist_ok=True)
         pyqt_extensions, extensions = [], []
         for ext in all_extensions:
-            if opts.only not in ('all', ext.name):
+            if opts.only not in {'all', ext.name}:
                 continue
             if not is_ext_allowed(self.compiling_for, ext):
                 continue
diff --git a/src/calibre/devices/kobo/driver.py b/src/calibre/devices/kobo/driver.py
index 2ae1976872..5fdc263187 100644
--- a/src/calibre/devices/kobo/driver.py
+++ b/src/calibre/devices/kobo/driver.py
@@ -709,7 +709,7 @@ class KOBO(USBMS):
             # for calibre's reference
             path = self._main_prefix + path + '.kobo'
             # print('Path: ' + path)
-        elif (ContentType in {'6', '10'}) and (
+        elif ContentType in {'6', '10'} and (
             MimeType == 'application/x-kobo-epub+zip' or (
             MimeType == 'application/epub+zip' and self.isTolinoDevice())
         ):
@@ -1797,7 +1797,7 @@ class KOBOTOUCH(KOBO):
                         allow_shelves = False
                         if show_debug:
                             debug_print('KoboTouch:update_booklist - have a deleted book')
-                    elif self.supports_kobo_archive() and (accessibility in {1, 2}):
+                    elif self.supports_kobo_archive() and accessibility in {1, 2}:
                         playlist_map[lpath].append('Archived')
                         allow_shelves = True
 
@@ -2192,7 +2192,7 @@ class KOBOTOUCH(KOBO):
 
         if oncard == 'cardb':
             print('path from_contentid cardb')
-        elif (ContentType in {'6', '10'}):
+        elif ContentType in {'6', '10'}:
             if (MimeType == 'application/octet-stream'):  # Audiobooks purchased from Kobo are in a different location.
                 path = self._main_prefix + KOBO_ROOT_DIR_NAME + '/audiobook/' + path
             elif (MimeType == 'audio/mpeg' and self.isTolinoDevice()):
diff --git a/src/calibre/ebooks/lrf/pylrs/pylrfopt.py b/src/calibre/ebooks/lrf/pylrs/pylrfopt.py
index d5b9d0ea68..2b07905f0e 100644
--- a/src/calibre/ebooks/lrf/pylrs/pylrfopt.py
+++ b/src/calibre/ebooks/lrf/pylrs/pylrfopt.py
@@ -2,7 +2,7 @@ def _optimize(tagList, tagName, conversion):
     # copy the tag of interest plus any text
     newTagList = []
     for tag in tagList:
-        if tag.name in (tagName, 'rawtext'):
+        if tag.name in {tagName, 'rawtext'}:
             newTagList.append(tag)
 
     # now, eliminate any duplicates (leaving the last one)
diff --git a/src/calibre/ebooks/mobi/reader/mobi6.py b/src/calibre/ebooks/mobi/reader/mobi6.py
index 9394cfea62..4270fa9f4a 100644
--- a/src/calibre/ebooks/mobi/reader/mobi6.py
+++ b/src/calibre/ebooks/mobi/reader/mobi6.py
@@ -862,7 +862,7 @@ class MobiReader:
             l = self.mobi_html.find(b'<', end)
             r = self.mobi_html.find(b'>', end)
             anchor = b'<a id="filepos%d"></a>'
-            if r > -1 and (r < l or l in (end, -1)):
+            if r > -1 and (r < l or l in {end, -1}):
                 p = self.mobi_html.rfind(b'<', 0, end + 1)
                 if (pos < end and p > -1 and not end_tag_re.match(self.mobi_html[p:r]) and
                         not self.mobi_html[p:r + 1].endswith(b'/>')):
diff --git a/src/calibre/ebooks/pdf/reflow.py b/src/calibre/ebooks/pdf/reflow.py
index b41781c29b..2c3c9b6229 100644
--- a/src/calibre/ebooks/pdf/reflow.py
+++ b/src/calibre/ebooks/pdf/reflow.py
@@ -278,7 +278,7 @@ class Text(Element):
             if m_self and m_other:
                 self.raw = m_self.group(1)
                 other.raw = m_other.group(1)
-        elif self.font_size_em not in (other.font_size_em, 1.0):
+        elif self.font_size_em not in {other.font_size_em, 1.0}:
             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
@@ -948,7 +948,12 @@ class Page:
                 t.tag = 'h2'  # It won't get set later
             # Centered if left and right margins are within FACTOR%
             # Because indents can waver a bit, use between indent_min and indent_max as == indent
-            if (lmargin < indent_min or lmargin > indent_max) and lmargin > left_max and lmargin not in (xmargin, ymargin) and lmargin >= rmargin - rmargin * CENTER_FACTOR and lmargin <= rmargin + rmargin * CENTER_FACTOR and '"float:right"' not in t.raw:
+            if (lmargin < indent_min or lmargin > indent_max) \
+              and lmargin > left_max \
+              and lmargin not in {xmargin, ymargin} \
+              and lmargin >= rmargin - rmargin*CENTER_FACTOR \
+              and lmargin <= rmargin + rmargin*CENTER_FACTOR \
+              and '"float:right"' not in t.raw:
                 # and t.left + t.width + t.left >= self.width + l_offset - t.average_character_width \
                 # and t.left + t.width + t.left <= self.width + l_offset + t.average_character_width:
                 t.align = 'C'
diff --git a/src/calibre/ebooks/pdf/render/serialize.py b/src/calibre/ebooks/pdf/render/serialize.py
index b4ba43ff48..8f19db1667 100644
--- a/src/calibre/ebooks/pdf/render/serialize.py
+++ b/src/calibre/ebooks/pdf/render/serialize.py
@@ -426,7 +426,7 @@ class PDFStream:
             if fmt == QImage.Format.Format_MonoLSB:
                 image = image.convertToFormat(QImage.Format.Format_Mono)
             fmt = QImage.Format.Format_Mono
-        elif (fmt not in (QImage.Format.Format_RGB32, QImage.Format.Format_ARGB32)):
+        elif fmt not in (QImage.Format.Format_RGB32, QImage.Format.Format_ARGB32):
             image = image.convertToFormat(QImage.Format.Format_ARGB32)
             fmt = QImage.Format.Format_ARGB32
 
diff --git a/src/calibre/ebooks/rtf2xml/inline.py b/src/calibre/ebooks/rtf2xml/inline.py
index 57a568c2cd..197890c412 100644
--- a/src/calibre/ebooks/rtf2xml/inline.py
+++ b/src/calibre/ebooks/rtf2xml/inline.py
@@ -400,7 +400,15 @@ class Inline:
                 for line in read_obj:
                     token = line[0:-1]
                     self.__token_info = ''
-                    if token in {'tx<mc<__________<rdblquote', 'tx<mc<__________<ldblquote', 'tx<mc<__________<lquote', 'tx<mc<__________<rquote', 'tx<mc<__________<emdash', 'tx<mc<__________<endash', 'tx<mc<__________<bullet'}:
+                    if token in {
+                        'tx<mc<__________<rdblquote',
+                        'tx<mc<__________<ldblquote',
+                        'tx<mc<__________<lquote',
+                        'tx<mc<__________<rquote',
+                        'tx<mc<__________<emdash',
+                        'tx<mc<__________<endash',
+                        'tx<mc<__________<bullet',
+                    }:
                         self.__token_info = 'text'
                     else:
                         self.__token_info = line[:16]
diff --git a/src/calibre/ebooks/rtf2xml/table.py b/src/calibre/ebooks/rtf2xml/table.py
index 86127e0f6d..d6542821aa 100644
--- a/src/calibre/ebooks/rtf2xml/table.py
+++ b/src/calibre/ebooks/rtf2xml/table.py
@@ -122,7 +122,12 @@ class Table:
             a row and start a cell.
         '''
         # 'cell'               : ('tb', 'cell______', self.default_func),
-        if self.__token_info in {'mi<mk<not-in-tbl', 'mi<mk<sect-start', 'mi<mk<sect-close', 'mi<mk<body-close'}:
+        if self.__token_info in {
+            'mi<mk<not-in-tbl',
+            'mi<mk<sect-start',
+            'mi<mk<sect-close',
+            'mi<mk<body-close',
+        }:
             self.__close_table(line)
         elif self.__token_info == 'mi<mk<pard-start':
             self.__start_row_func(line)
@@ -423,7 +428,12 @@ class Table:
         '''
         # cw<tb<cell______<nu<true
         # mi<mk<sect-start
-        if self.__token_info in {'mi<mk<not-in-tbl', 'mi<mk<sect-start', 'mi<mk<sect-close', 'mi<mk<body-close'}:
+        if self.__token_info in {
+            'mi<mk<not-in-tbl',
+            'mi<mk<sect-start',
+            'mi<mk<sect-close',
+            'mi<mk<body-close',
+        }:
             self.__end_cell_func(line)
             self.__end_row_func(line)
             self.__close_table(line)
@@ -450,7 +460,12 @@ class Table:
         self.__write_obj.write('mi<mk<closecell_\n')
 
     def __in_row_func(self, line):
-        if self.__token_info in {'mi<mk<not-in-tbl', 'mi<mk<sect-start', 'mi<mk<sect-close', 'mi<mk<body-close'}:
+        if self.__token_info in {
+            'mi<mk<not-in-tbl',
+            'mi<mk<sect-start',
+            'mi<mk<sect-close',
+            'mi<mk<body-close',
+        }:
             self.__end_row_func(line)
             self.__close_table(line)
             self.__write_obj.write(line)
diff --git a/src/calibre/utils/imghdr.py b/src/calibre/utils/imghdr.py
index 0755024623..74d3874740 100644
--- a/src/calibre/utils/imghdr.py
+++ b/src/calibre/utils/imghdr.py
@@ -147,7 +147,7 @@ def jpeg_dimensions(stream):
         while marker == 0xff:
             marker = read_byte()
         q = marker
-        if 192 <= q <= 207 and q not in {196, 204}:
+        if 0xc0 <= q <= 0xcf and q not in {0xc4, 0xcc}:
             # SOFn marker
             stream.seek(3, os.SEEK_CUR)
             return unpack(b'>HH', read(4))