diff --git a/manual/conf.py b/manual/conf.py
index ad61dcbde0..3702a507c1 100644
--- a/manual/conf.py
+++ b/manual/conf.py
@@ -47,11 +47,11 @@ templates_path = ['templates']
 source_suffix = {'.rst': 'restructuredtext'}
 
 # The master toctree document.
-master_doc = 'index' if tags.has('online') else 'simple_index'
+master_doc = 'index' if tags.has('online') else 'simple_index'  # noqa: F821
 # kill the warning about index/simple_index not being in a toctree
 exclude_patterns = ['simple_index.rst'] if master_doc == 'index' else ['index.rst']
 exclude_patterns.append('cli-options-header.rst')
-if tags.has('gettext'):
+if tags.has('gettext'):  # noqa: F821
     # Do not exclude anything as the strings must be translated. This will
     # generate a warning about the documents not being in a toctree, just ignore
     # it.
diff --git a/manual/plugin_examples/editor_demo/main.py b/manual/plugin_examples/editor_demo/main.py
index 3cb48e147a..3da2fb442d 100644
--- a/manual/plugin_examples/editor_demo/main.py
+++ b/manual/plugin_examples/editor_demo/main.py
@@ -32,7 +32,7 @@ class DemoTool(Tool):
     def create_action(self, for_toolbar=True):
         # Create an action, this will be added to the plugins toolbar and
         # the plugins menu
-        ac = QAction(get_icons('images/icon.png'), 'Magnify fonts', self.gui)
+        ac = QAction(get_icons('images/icon.png'), 'Magnify fonts', self.gui)  # noqa: F821
         if not for_toolbar:
             # Register a keyboard shortcut for this toolbar action. We only
             # register it for the action created for the menu, not the toolbar,
diff --git a/recipes/daum_net.recipe b/recipes/daum_net.recipe
index 7c72996b56..f840c15254 100644
--- a/recipes/daum_net.recipe
+++ b/recipes/daum_net.recipe
@@ -61,7 +61,7 @@ class MediaDaumRecipe(BasicNewsRecipe):
             lambda match: '<em>'),
         (re.compile(r'<i>(<br[^>]*>[ \t\r\n]*)*', re.DOTALL | re.IGNORECASE),
             lambda match: '<i>'),
-        (re.compile(u'(<br[^>]*>[ \t\r\n]*)*(\u25B6|\u25CF|\u261E|\u24D2|\(c\))*\[[^\]]*(\u24D2|\(c\)|\uAE30\uC0AC|\uC778\uAE30[^\]]*\uB274\uC2A4)[^\]]*\].*</div>', re.DOTALL | re.IGNORECASE),  # noqa: E501
+        (re.compile(u'(<br[^>]*>[ \t\r\n]*)*(\u25B6|\u25CF|\u261E|\u24D2|\(c\))*\[[^\]]*(\u24D2|\(c\)|\uAE30\uC0AC|\uC778\uAE30[^\]]*\uB274\uC2A4)[^\]]*\].*</div>', re.DOTALL | re.IGNORECASE),  # noqa: E501, W605
             lambda match: '</div>'),
     ]
 
diff --git a/recipes/nytimes.recipe b/recipes/nytimes.recipe
index 4dd1f033c1..0ab2454b53 100644
--- a/recipes/nytimes.recipe
+++ b/recipes/nytimes.recipe
@@ -7,7 +7,7 @@ from __future__ import absolute_import, division, print_function, unicode_litera
 import datetime
 import json
 import re
-from pprint import pprint
+from pprint import pprint  # noqa: F401
 
 from calibre import strftime
 from calibre.ebooks.BeautifulSoup import Tag
diff --git a/recipes/nytimes_sub.recipe b/recipes/nytimes_sub.recipe
index d0566257ec..cbed02b28b 100644
--- a/recipes/nytimes_sub.recipe
+++ b/recipes/nytimes_sub.recipe
@@ -7,7 +7,7 @@ from __future__ import absolute_import, division, print_function, unicode_litera
 import datetime
 import json
 import re
-from pprint import pprint
+from pprint import pprint  # noqa: F401
 
 from calibre import strftime
 from calibre.ebooks.BeautifulSoup import Tag
diff --git a/src/calibre/db/tests/main.py b/src/calibre/db/tests/main.py
index eb5093a175..19c2d80689 100644
--- a/src/calibre/db/tests/main.py
+++ b/src/calibre/db/tests/main.py
@@ -14,7 +14,7 @@ def find_tests():
 
 if __name__ == '__main__':
     try:
-        import init_calibre
+        import init_calibre  # noqa: F401
     except ImportError:
         pass
     run_tests(find_tests)
diff --git a/src/calibre/ebooks/BeautifulSoup.py b/src/calibre/ebooks/BeautifulSoup.py
index 857911185f..0306314cfe 100644
--- a/src/calibre/ebooks/BeautifulSoup.py
+++ b/src/calibre/ebooks/BeautifulSoup.py
@@ -3,7 +3,7 @@
 
 
 import bs4
-from bs4 import CData, Comment, Declaration, NavigableString, ProcessingInstruction, SoupStrainer, Tag, __version__
+from bs4 import CData, Comment, Declaration, NavigableString, ProcessingInstruction, SoupStrainer, Tag, __version__  # noqa: F401
 
 
 def parse_html(markup):
diff --git a/src/calibre/ebooks/conversion/plugins/pdf_output.py b/src/calibre/ebooks/conversion/plugins/pdf_output.py
index e8e1657e95..a1dcee7f18 100644
--- a/src/calibre/ebooks/conversion/plugins/pdf_output.py
+++ b/src/calibre/ebooks/conversion/plugins/pdf_output.py
@@ -151,7 +151,7 @@ class PDFOutput(OutputFormatPlugin):
         # Ensure Qt is setup to be used with WebEngine
         # specialize_options is called early enough in the pipeline
         # that hopefully no Qt application has been constructed as yet
-        from qt.webengine import QWebEnginePage
+        from qt.webengine import QWebEnginePage  # noqa: I001, F401
         from calibre.gui2 import must_use_qt
         from calibre.utils.webengine import setup_fake_protocol, setup_default_profile
         setup_fake_protocol()
diff --git a/src/calibre/ebooks/conversion/plumber.py b/src/calibre/ebooks/conversion/plumber.py
index a0b2ad17a3..69dcdcf9ec 100644
--- a/src/calibre/ebooks/conversion/plumber.py
+++ b/src/calibre/ebooks/conversion/plumber.py
@@ -1073,7 +1073,7 @@ OptionRecommendation(name='search_replace',
         self.flush()
         if self.opts.embed_all_fonts or self.opts.embed_font_family:
             # Start the threaded font scanner now, for performance
-            from calibre.utils.fonts.scanner import font_scanner
+            from calibre.utils.fonts.scanner import font_scanner  # noqa: F401
         import logging
 
         import css_parser
diff --git a/src/calibre/ebooks/metadata/opf3_test.py b/src/calibre/ebooks/metadata/opf3_test.py
index 81651cfca0..ebb265027c 100644
--- a/src/calibre/ebooks/metadata/opf3_test.py
+++ b/src/calibre/ebooks/metadata/opf3_test.py
@@ -58,7 +58,7 @@ from calibre.ebooks.metadata.opf3 import (
 )
 
 # This import is needed to prevent a test from running slowly
-from calibre.ebooks.oeb.polish.pretty import pretty_opf, pretty_xml_tree
+from calibre.ebooks.oeb.polish.pretty import pretty_opf, pretty_xml_tree  # noqa: F401
 from calibre.utils.xml_parse import safe_xml_fromstring
 
 read_user_categories, set_user_categories, read_link_maps, set_link_maps
diff --git a/src/calibre/ebooks/oeb/polish/tests/main.py b/src/calibre/ebooks/oeb/polish/tests/main.py
index 67c21f61ec..91540bc232 100644
--- a/src/calibre/ebooks/oeb/polish/tests/main.py
+++ b/src/calibre/ebooks/oeb/polish/tests/main.py
@@ -13,7 +13,7 @@ def find_tests():
 
 if __name__ == '__main__':
     try:
-        import init_calibre
+        import init_calibre  # noqa: F401
     except ImportError:
         pass
     run_tests(find_tests)
diff --git a/src/calibre/ebooks/oeb/transforms/subset.py b/src/calibre/ebooks/oeb/transforms/subset.py
index 7985786743..01f1a1bd92 100644
--- a/src/calibre/ebooks/oeb/transforms/subset.py
+++ b/src/calibre/ebooks/oeb/transforms/subset.py
@@ -302,7 +302,7 @@ class SubsetFonts:
 
     def find_chars(self, elem, style):
         ans = set()
-        transform = lambda x: x
+        transform = lambda x: x  # noqa: E731
         tt = style.get('text-transform')
         if tt:
             if tt in ('uppercase', 'capitalize'):
diff --git a/src/calibre/ebooks/txt/markdownml.py b/src/calibre/ebooks/txt/markdownml.py
index c91326bec7..9b418f6e5e 100644
--- a/src/calibre/ebooks/txt/markdownml.py
+++ b/src/calibre/ebooks/txt/markdownml.py
@@ -86,7 +86,7 @@ class MarkdownMLizer(OEB2HTML):
         # Condense redundant spaces created by replacing newlines with spaces.
         text = re.sub(r'[ ]{2,}', ' ', text)
         text = re.sub(r'\t+', '', text)
-        if self.remove_space_after_newline == True:
+        if self.remove_space_after_newline == True:  # noqa: E712
             text = re.sub(r'^ +', '', text)
             self.remove_space_after_newline = False
         return text
@@ -148,13 +148,13 @@ class MarkdownMLizer(OEB2HTML):
 
         if style['font-style'] == 'italic' or tag in ('i', 'em'):
             if tag not in ('h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'cite'):
-                if self.style_italic == False:
+                if self.style_italic == False:  # noqa: E712
                     text.append('*')
                     tags.append('*')
                     self.style_italic = True
         if style['font-weight'] in ('bold', 'bolder') or tag in ('b', 'strong'):
             if tag not in ('h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'th'):
-                if self.style_bold == False:
+                if self.style_bold == False:  # noqa: E712
                     text.append('**')
                     tags.append('**')
                     self.style_bold = True
diff --git a/src/calibre/ebooks/txt/textileml.py b/src/calibre/ebooks/txt/textileml.py
index d1dc782e40..09b7ecfaf3 100644
--- a/src/calibre/ebooks/txt/textileml.py
+++ b/src/calibre/ebooks/txt/textileml.py
@@ -138,7 +138,7 @@ class TextileMLizer(OEB2HTML):
         # Condense redundant spaces created by replacing newlines with spaces.
         text = re.sub(r'[ ]{2,}', ' ', text)
         text = re.sub(r'\t+', '', text)
-        if self.remove_space_after_newline == True:
+        if self.remove_space_after_newline == True:  # noqa: E712
             text = re.sub(r'^ +', '', text)
             self.remove_space_after_newline = False
         return text
@@ -268,7 +268,7 @@ class TextileMLizer(OEB2HTML):
 
         if style['font-style'] == 'italic' or tag in ('i', 'em'):
             if tag not in ('h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'cite'):
-                if self.style_italic == False:
+                if self.style_italic == False:  # noqa: E712
                     if self.in_a_link:
                         text.append('_')
                         tags.append('_')
@@ -279,7 +279,7 @@ class TextileMLizer(OEB2HTML):
                     self.style_italic = True
         if style['font-weight'] in ('bold', 'bolder') or tag in ('b', 'strong'):
             if tag not in ('h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'th'):
-                if self.style_bold == False:
+                if self.style_bold == False:  # noqa: E712
                     if self.in_a_link:
                         text.append('*')
                         tags.append('*')
@@ -290,13 +290,13 @@ class TextileMLizer(OEB2HTML):
                     self.style_bold = True
         if style['text-decoration'] == 'underline' or tag in ('u', 'ins'):
             if tag != 'a':
-                if self.style_under == False:
+                if self.style_under == False:  # noqa: E712
                     text.append('[+')
                     tags.append('+]')
                     self.style_embed.append('+')
                     self.style_under = True
         if style['text-decoration'] == 'line-through' or tag in ('strike', 'del', 's'):
-            if self.style_strike == False:
+            if self.style_strike == False:  # noqa: E712
                 text.append('[-')
                 tags.append('-]')
                 self.style_embed.append('-')
@@ -423,12 +423,12 @@ class TextileMLizer(OEB2HTML):
             tags.append('')
         elif tag == 'span':
             if style['font-variant'] == 'small-caps':
-                if self.style_smallcap == False:
+                if self.style_smallcap == False:  # noqa: E712
                     text.append('&')
                     tags.append('&')
                     self.style_smallcap = True
             else:
-                if self.in_a_link == False:
+                if self.in_a_link == False:  # noqa: E712
                     txt = '%'
                     if self.opts.keep_links:
                         txt += self.check_id_tag(attribs)
diff --git a/src/calibre/gui2/store/config/chooser/models.py b/src/calibre/gui2/store/config/chooser/models.py
index b6f1ed736c..c4dd83dd18 100644
--- a/src/calibre/gui2/store/config/chooser/models.py
+++ b/src/calibre/gui2/store/config/chooser/models.py
@@ -266,14 +266,14 @@ class SearchFilter(SearchQueryParser):
                 accessor = q[locvalue]
                 if query == 'true':
                     if locvalue in ('affiliate', 'drm', 'enabled'):
-                        if accessor(sr) == True:
+                        if accessor(sr) == True:  # noqa: E712
                             matches.add(sr)
                     elif accessor(sr) is not None:
                         matches.add(sr)
                     continue
                 if query == 'false':
                     if locvalue in ('affiliate', 'drm', 'enabled'):
-                        if accessor(sr) == False:
+                        if accessor(sr) == False:  # noqa: E712
                             matches.add(sr)
                     elif accessor(sr) is None:
                         matches.add(sr)
diff --git a/src/calibre/gui2/tweak_book/editor/syntax/xml.py b/src/calibre/gui2/tweak_book/editor/syntax/xml.py
index 98b0954cc3..dd5a6fa598 100644
--- a/src/calibre/gui2/tweak_book/editor/syntax/xml.py
+++ b/src/calibre/gui2/tweak_book/editor/syntax/xml.py
@@ -4,4 +4,4 @@
 __license__ = 'GPL v3'
 __copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'
 
-from calibre.gui2.tweak_book.editor.syntax.html import XMLHighlighter as Highlighter
+from calibre.gui2.tweak_book.editor.syntax.html import XMLHighlighter as Highlighter  # noqa: F401
diff --git a/src/calibre/gui2/tweak_book/editor/widget.py b/src/calibre/gui2/tweak_book/editor/widget.py
index 1c64a7554e..d7b50e9a57 100644
--- a/src/calibre/gui2/tweak_book/editor/widget.py
+++ b/src/calibre/gui2/tweak_book/editor/widget.py
@@ -650,7 +650,7 @@ def launch_editor(path_to_edit, path_is_raw=False, syntax='html', callback=None)
     opts = option_parser().parse_args([])
     app = Application([])
     # Create the actions that are placed into the editors toolbars
-    main = Main(opts)
+    main = Main(opts)  # noqa: F841
     if path_is_raw:
         raw = path_to_edit
     else:
diff --git a/src/calibre/srv/tests/main.py b/src/calibre/srv/tests/main.py
index 829ba97cd0..e6f8ae5ec2 100644
--- a/src/calibre/srv/tests/main.py
+++ b/src/calibre/srv/tests/main.py
@@ -13,7 +13,7 @@ def find_tests():
 
 if __name__ == '__main__':
     try:
-        import init_calibre
+        import init_calibre  # noqa: F401
     except ImportError:
         pass
     run_tests(find_tests)
diff --git a/src/calibre/test_build.py b/src/calibre/test_build.py
index b7162c0209..082310ca7a 100644
--- a/src/calibre/test_build.py
+++ b/src/calibre/test_build.py
@@ -106,8 +106,8 @@ class BuildTest(unittest.TestCase):
         self.assertEqual(data, decompress(cdata))
 
     def test_html5lib(self):
-        import html5lib.html5parser
-        from html5lib import parse
+        import html5lib.html5parser  # noqa: F401
+        from html5lib import parse  # noqa: F401
 
     def test_html5_parser(self):
         from html5_parser import parse
diff --git a/src/calibre/utils/ipython.py b/src/calibre/utils/ipython.py
index f66bcbbc4b..5e18af640e 100644
--- a/src/calibre/utils/ipython.py
+++ b/src/calibre/utils/ipython.py
@@ -172,14 +172,14 @@ def simple_repl(user_ns={}):
         setup_pyreadline()
     else:
         try:
-            import rlcompleter
+            import rlcompleter  # noqa: I001, F401
             import readline
             readline.parse_and_bind("tab: complete")
         except ImportError:
             pass
 
     user_ns = user_ns or {}
-    import sys, re
+    import sys, re  # noqa: I001, E401, F401
     for x in ('os', 'sys', 're'):
         user_ns[x] = user_ns.get(x, globals().get(x, locals().get(x)))
     user_ns['exit'] = Exit()