diff --git a/recipes/daum_net.recipe b/recipes/daum_net.recipe
index 97b17e7016..a6590bb2d5 100644
--- a/recipes/daum_net.recipe
+++ b/recipes/daum_net.recipe
@@ -45,7 +45,7 @@ class MediaDaumRecipe(BasicNewsRecipe):
             lambda match: '</em>'),
         (re.compile(r'(<br[^>]*>[ \t\r\n]*)*</i>', re.DOTALL | re.IGNORECASE),
             lambda match: '</i>'),
-        (re.compile(u'\(\uB05D\)[ \t\r\n]*<br[^>]*>.*</div>', re.DOTALL | re.IGNORECASE),
+        (re.compile(r'\(\uB05D\)[ \t\r\n]*<br[^>]*>.*</div>', re.DOTALL | re.IGNORECASE),
             lambda match: '</div>'),
         (re.compile(r'(<br[^>]*>[ \t\r\n]*)*<div', re.DOTALL | re.IGNORECASE),
             lambda match: '<div'),
diff --git a/recipes/la_stampa.recipe b/recipes/la_stampa.recipe
index 69767fba37..820016c60e 100644
--- a/recipes/la_stampa.recipe
+++ b/recipes/la_stampa.recipe
@@ -35,8 +35,8 @@ class LaStampa(BasicNewsRecipe):
 
     keep_only_tags = [
         dict(attrs={'class': ['boxocchiello2', 'titoloRub', 'titologir', 'autore-girata', 'luogo-girata', 'catenaccio', 'sezione', 'articologirata', 'bodytext', 'news-single-img', 'ls-articoloCorpo', 'ls-blog-list-1col']}),  # noqa
-                      dict(name='div', attrs={'id': 'corpoarticolo'})
-                      ]
+        dict(name='div', attrs={'id': 'corpoarticolo'})
+    ]
 
     remove_tags = [dict(name='div', attrs={'id': ['menutop', 'fwnetblocco']}),
                    dict(
diff --git a/src/calibre/devices/cli.py b/src/calibre/devices/cli.py
index c34afc4dc2..722ee0ce50 100755
--- a/src/calibre/devices/cli.py
+++ b/src/calibre/devices/cli.py
@@ -267,7 +267,7 @@ def main():
             parser = OptionParser(usage="usage: %prog ls [options] path\nList files on the device\n\npath must begin with / or card:/")
             parser.add_option(
                 "-l", help="In addition to the name of each file, print the file type, permissions, and  timestamp  (the  modification time, in the local timezone). Times are local.",  # noqa
-                              dest="ll", action="store_true", default=False)
+                dest="ll", action="store_true", default=False)
             parser.add_option("-R", help="Recursively list subdirectories encountered. /dev and /proc are omitted",
                               dest="recurse", action="store_true", default=False)
             parser.remove_option("-h")
diff --git a/src/calibre/ebooks/metadata/sources/ozon.py b/src/calibre/ebooks/metadata/sources/ozon.py
index 9513a9af10..271423715a 100644
--- a/src/calibre/ebooks/metadata/sources/ozon.py
+++ b/src/calibre/ebooks/metadata/sources/ozon.py
@@ -64,7 +64,7 @@ class Ozon(Source):
         res = None
         if ozon_id:
             # no affiliateId is used in search/detail
-            url = '{}/context/detail/id/{}'.format(self.ozon_url, quote(ozon_id), _get_affiliateId())
+            url = '{}/context/detail/id/{}'.format(self.ozon_url, quote(ozon_id))
             res = ('ozon', ozon_id, url)
         return res
 
diff --git a/src/calibre/ebooks/mobi/writer8/index.py b/src/calibre/ebooks/mobi/writer8/index.py
index 87555502fb..c2f0ffa1c8 100644
--- a/src/calibre/ebooks/mobi/writer8/index.py
+++ b/src/calibre/ebooks/mobi/writer8/index.py
@@ -129,7 +129,7 @@ class Index(object):  # {{{
                 shifts = mask_to_bit_shifts[mask]
                 ans |= mask & (nentries << shifts)
             if len(cbs) != cls.control_byte_count:
-                raise ValueError('The entry %r is invalid'%[lead_text, tags])
+                raise ValueError('The entry {!r} is invalid'.format([lead_text, tags]))
             control_bytes.append(cbs)
         return control_bytes
 
diff --git a/src/calibre/srv/render_book.py b/src/calibre/srv/render_book.py
index 5a0e1aa3b1..e92759e8b6 100644
--- a/src/calibre/srv/render_book.py
+++ b/src/calibre/srv/render_book.py
@@ -144,7 +144,7 @@ def transform_declaration(decl):
     changed = False
     nonstandard_writing_mode_props = {}
     standard_writing_mode_props = {}
-    
+
     for prop, parent_prop in tuple(decl):
         if prop.name in page_break_properties:
             changed = True
diff --git a/src/pyj/read_book/iframe.pyj b/src/pyj/read_book/iframe.pyj
index 181bc76591..e06ce71c79 100644
--- a/src/pyj/read_book/iframe.pyj
+++ b/src/pyj/read_book/iframe.pyj
@@ -4,7 +4,7 @@ from __python__ import bound_methods, hash_literals
 
 import traceback
 from gettext import gettext as _
-from select import selection_extents, move_end_of_selection, word_at_point
+from select import move_end_of_selection, selection_extents, word_at_point
 
 from fs_images import fix_fullscreen_svg_images
 from iframe_comm import IframeClient
@@ -12,20 +12,17 @@ from range_utils import (
     highlight_associated_with_selection, reset_highlight_counter, select_crw,
     unwrap_all_crw, unwrap_crw, wrap_text_in_range
 )
-from read_book.cfi import (
-    cfi_for_selection, range_from_cfi, scroll_to as scroll_to_cfi
-)
+from read_book.cfi import cfi_for_selection, range_from_cfi
 from read_book.extract import get_elements
 from read_book.find import reset_find_caches, select_search_result
 from read_book.flow_mode import (
     anchor_funcs as flow_anchor_funcs, auto_scroll_action as flow_auto_scroll_action,
     cancel_drag_scroll as cancel_drag_scroll_flow, ensure_selection_visible,
     flow_onwheel, flow_to_scroll_fraction, handle_gesture as flow_handle_gesture,
-    handle_shortcut as flow_handle_shortcut, layout as flow_layout,
-    scroll_by_page as flow_scroll_by_page,
+    handle_shortcut as flow_handle_shortcut, jump_to_cfi as flow_jump_to_cfi,
+    layout as flow_layout, scroll_by_page as flow_scroll_by_page,
     scroll_to_extend_annotation as flow_annotation_scroll,
-    start_drag_scroll as start_drag_scroll_flow,
-    jump_to_cfi as flow_jump_to_cfi
+    start_drag_scroll as start_drag_scroll_flow
 )
 from read_book.footnotes import is_footnote_link
 from read_book.globals import (
diff --git a/src/pyj/read_book/paged_mode.pyj b/src/pyj/read_book/paged_mode.pyj
index 7604bace5e..0c554abb55 100644
--- a/src/pyj/read_book/paged_mode.pyj
+++ b/src/pyj/read_book/paged_mode.pyj
@@ -284,8 +284,6 @@ def layout(is_single_page, on_resize):
         nonlocal number_of_cols
         ncols = number_of_cols = (scroll_viewport.paged_content_inline_size() + gap) / col_and_gap
         if ncols is not Math.floor(ncols):
-            n = number_of_cols = Math.floor(ncols)
-            dw = n*col_size + (n-1)*gap
             data = {'col_size':col_size, 'gap':gap, 'scrollWidth':scroll_viewport.paged_content_inline_size(), 'ncols':ncols, 'desired_inline_size':dis}
             return data
 
@@ -458,7 +456,7 @@ def scroll_to_elem(elem):
             # elem.scrollIntoView(). However, in some cases it gives
             # inaccurate results, so we prefer the bounding client rect,
             # when possible.
-            
+
             # In horizontal writing, the inline start position depends on the direction
             if scroll_viewport.horizontal_writing_mode:
                 inline_start = elem.scrollLeft if scroll_viewport.ltr else elem.scrollRight