diff --git a/src/calibre/ebooks/metadata/book/base.py b/src/calibre/ebooks/metadata/book/base.py
index ed6b15e1e0..a7afd67f46 100644
--- a/src/calibre/ebooks/metadata/book/base.py
+++ b/src/calibre/ebooks/metadata/book/base.py
@@ -16,6 +16,7 @@ from calibre.ebooks.metadata.book import (
 )
 from calibre.library.field_metadata import FieldMetadata
 from calibre.utils.icu import lower as icu_lower, sort_key
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems, string_or_bytes
 
 # Special sets used to optimize the performance of getting and setting
diff --git a/src/calibre/ebooks/oeb/base.py b/src/calibre/ebooks/oeb/base.py
index 746f7133ef..a0ef201374 100644
--- a/src/calibre/ebooks/oeb/base.py
+++ b/src/calibre/ebooks/oeb/base.py
@@ -6,25 +6,32 @@ __license__   = 'GPL v3'
 __copyright__ = '2008, Marshall T. Vandegrift <llasram@gmail.com>'
 __docformat__ = 'restructuredtext en'
 
-import os, re, logging, sys, numbers
+import logging
+import numbers
+import os
+import re
+import sys
 from collections import defaultdict
 from itertools import count
+from lxml import etree, html
 from operator import attrgetter
 
-from lxml import etree, html
-from calibre import force_unicode
-from calibre.constants import filesystem_encoding, __version__
-from calibre.translations.dynamic import translate
-from calibre.utils.xml_parse import safe_xml_fromstring
+from calibre import as_unicode, force_unicode, get_types_map, isbytestring
+from calibre.constants import __version__, filesystem_encoding
 from calibre.ebooks.chardet import xml_to_unicode
 from calibre.ebooks.conversion.preprocess import CSSPreProcessor
-from calibre import (isbytestring, as_unicode, get_types_map)
-from calibre.ebooks.oeb.parse_utils import barename, XHTML_NS, namespace, XHTML, parse_html, NotHTML
+from calibre.ebooks.oeb.parse_utils import (
+    XHTML, XHTML_NS, NotHTML, barename, namespace, parse_html,
+)
+from calibre.translations.dynamic import translate
 from calibre.utils.cleantext import clean_xml_chars
+from calibre.utils.icu import numeric_sort_key, title_case as icu_title
 from calibre.utils.short_uuid import uuid4
-from polyglot.builtins import iteritems, string_or_bytes, itervalues, codepoint_to_chr
-from polyglot.urllib import unquote as urlunquote, urldefrag, urljoin, urlparse, urlunparse
-from calibre.utils.icu import numeric_sort_key
+from calibre.utils.xml_parse import safe_xml_fromstring
+from polyglot.builtins import codepoint_to_chr, iteritems, itervalues, string_or_bytes
+from polyglot.urllib import (
+    unquote as urlunquote, urldefrag, urljoin, urlparse, urlunparse,
+)
 
 XML_NS       = 'http://www.w3.org/XML/1998/namespace'
 OEB_DOC_NS   = 'http://openebook.org/namespaces/oeb-document/1.0/'
@@ -249,7 +256,7 @@ def rewrite_links(root, link_repl_func, resolve_base_href=False):
     If the ``link_repl_func`` returns None, the attribute or
     tag text will be removed completely.
     '''
-    from css_parser import replaceUrls, log, CSSParser
+    from css_parser import CSSParser, log, replaceUrls
     log.setLevel(logging.WARN)
     log.raiseExceptions = False
 
diff --git a/src/calibre/ebooks/oeb/polish/css.py b/src/calibre/ebooks/oeb/polish/css.py
index 8155eaeee5..37db8222f5 100644
--- a/src/calibre/ebooks/oeb/polish/css.py
+++ b/src/calibre/ebooks/oeb/polish/css.py
@@ -17,6 +17,7 @@ from calibre.ebooks.oeb.polish.pretty import (
     pretty_script_or_style, pretty_xml_tree, serialize,
 )
 from calibre.utils.icu import lower as icu_lower, numeric_sort_key
+from calibre.utils.localization import ngettext
 from css_selectors import Select, SelectorError, SelectorSyntaxError, parse
 from polyglot.builtins import iteritems, itervalues
 from polyglot.functools import lru_cache
diff --git a/src/calibre/ebooks/oeb/transforms/jacket.py b/src/calibre/ebooks/oeb/transforms/jacket.py
index 9b1b0fb27a..0add5bfb72 100644
--- a/src/calibre/ebooks/oeb/transforms/jacket.py
+++ b/src/calibre/ebooks/oeb/transforms/jacket.py
@@ -24,6 +24,7 @@ from calibre.library.comments import comments_to_html, markdown
 from calibre.utils.config import tweaks
 from calibre.utils.date import as_local_time, format_date, is_date_undefined
 from calibre.utils.icu import sort_key
+from calibre.utils.localization import ngettext
 from calibre.utils.resources import get_path as P
 
 JACKET_XPATH = '//h:meta[@name="calibre-content" and @content="jacket"]'
diff --git a/src/calibre/ebooks/oeb/transforms/manglecase.py b/src/calibre/ebooks/oeb/transforms/manglecase.py
index 835c1939d3..c2f76239d2 100644
--- a/src/calibre/ebooks/oeb/transforms/manglecase.py
+++ b/src/calibre/ebooks/oeb/transforms/manglecase.py
@@ -9,7 +9,9 @@ from lxml import etree
 
 from calibre.ebooks.oeb.base import CSS_MIME, XHTML, XHTML_NS, namespace
 from calibre.ebooks.oeb.stylizer import Stylizer
-from calibre.utils.icu import lower as icu_lower, upper as icu_upper
+from calibre.utils.icu import (
+    lower as icu_lower, title_case as icu_title, upper as icu_upper,
+)
 from polyglot.builtins import string_or_bytes
 
 CASE_MANGLER_CSS = """
diff --git a/src/calibre/gui2/actions/add.py b/src/calibre/gui2/actions/add.py
index e9b0b55fbc..d2bc9bcd53 100644
--- a/src/calibre/gui2/actions/add.py
+++ b/src/calibre/gui2/actions/add.py
@@ -15,8 +15,8 @@ from calibre.constants import iswindows
 from calibre.ebooks import BOOK_EXTENSIONS
 from calibre.ebooks.metadata import MetaInformation, normalize_isbn
 from calibre.gui2 import (
-    choose_dir, choose_files, choose_files_and_remember_all_files, error_dialog,
-    gprefs, info_dialog, question_dialog, warning_dialog
+    choose_dir, choose_files, choose_files_and_remember_all_files, error_dialog, gprefs,
+    info_dialog, question_dialog, warning_dialog,
 )
 from calibre.gui2.actions import InterfaceAction
 from calibre.gui2.dialogs.add_empty_book import AddEmptyBookDialog
@@ -26,6 +26,7 @@ from calibre.ptempfile import PersistentTemporaryFile
 from calibre.utils.config_base import tweaks
 from calibre.utils.filenames import ascii_filename, make_long_path_useable
 from calibre.utils.icu import sort_key
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems, string_or_bytes
 
 
diff --git a/src/calibre/gui2/actions/author_mapper.py b/src/calibre/gui2/actions/author_mapper.py
index efa842b4a8..abc25fcb06 100644
--- a/src/calibre/gui2/actions/author_mapper.py
+++ b/src/calibre/gui2/actions/author_mapper.py
@@ -3,8 +3,10 @@
 
 
 from qt.core import QDialog
+
 from calibre.gui2 import gprefs
 from calibre.gui2.actions import InterfaceAction
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems
 
 
@@ -27,7 +29,7 @@ class AuthorMapAction(InterfaceAction):
         self.do_map(ids, selected)
 
     def do_map(self, book_ids, selected):
-        from calibre.ebooks.metadata.author_mapper import map_authors, compile_rules
+        from calibre.ebooks.metadata.author_mapper import compile_rules, map_authors
         from calibre.gui2.author_mapper import RulesDialog
         from calibre.gui2.widgets import BusyCursor
         d = RulesDialog(self.gui)
diff --git a/src/calibre/gui2/actions/choose_library.py b/src/calibre/gui2/actions/choose_library.py
index a1e08f687e..e68fe447f9 100644
--- a/src/calibre/gui2/actions/choose_library.py
+++ b/src/calibre/gui2/actions/choose_library.py
@@ -9,25 +9,26 @@ import posixpath
 import sys
 import weakref
 from contextlib import suppress
-from functools import partial, lru_cache
+from functools import lru_cache, partial
 from qt.core import (
     QAction, QCoreApplication, QDialog, QDialogButtonBox, QGridLayout, QIcon,
-    QInputDialog, QLabel, QLineEdit, QMenu, QSize, Qt, QTimer, QToolButton,
-    QVBoxLayout, pyqtSignal
+    QInputDialog, QLabel, QLineEdit, QMenu, QSize, Qt, QTimer, QToolButton, QVBoxLayout,
+    pyqtSignal,
 )
 
 from calibre import isbytestring, sanitize_file_name
 from calibre.constants import (
-    config_dir, filesystem_encoding, get_portable_base, isportable, iswindows
+    config_dir, filesystem_encoding, get_portable_base, isportable, iswindows,
 )
 from calibre.gui2 import (
     Dispatcher, choose_dir, choose_images, error_dialog, gprefs, info_dialog,
-    open_local_file, pixmap_to_data, question_dialog, warning_dialog
+    open_local_file, pixmap_to_data, question_dialog, warning_dialog,
 )
 from calibre.gui2.actions import InterfaceAction
 from calibre.library import current_library_name
 from calibre.utils.config import prefs, tweaks
 from calibre.utils.icu import sort_key
+from calibre.utils.localization import ngettext
 
 
 def db_class():
diff --git a/src/calibre/gui2/actions/convert.py b/src/calibre/gui2/actions/convert.py
index bf52e9aa7d..0cfd8c39b1 100644
--- a/src/calibre/gui2/actions/convert.py
+++ b/src/calibre/gui2/actions/convert.py
@@ -7,14 +7,14 @@ __docformat__ = 'restructuredtext en'
 
 import os
 from functools import partial
-
 from qt.core import QModelIndex, QTimer
 
-from calibre.gui2 import error_dialog, Dispatcher, gprefs
-from calibre.gui2.tools import convert_single_ebook, convert_bulk_ebook
-from calibre.utils.config import prefs, tweaks
-from calibre.gui2.actions import InterfaceAction
 from calibre.customize.ui import plugin_for_input_format
+from calibre.gui2 import Dispatcher, error_dialog, gprefs
+from calibre.gui2.actions import InterfaceAction
+from calibre.gui2.tools import convert_bulk_ebook, convert_single_ebook
+from calibre.utils.config import prefs, tweaks
+from calibre.utils.localization import ngettext
 
 
 class ConvertAction(InterfaceAction):
diff --git a/src/calibre/gui2/actions/copy_to_library.py b/src/calibre/gui2/actions/copy_to_library.py
index 02929721d6..fbbbf92ad8 100644
--- a/src/calibre/gui2/actions/copy_to_library.py
+++ b/src/calibre/gui2/actions/copy_to_library.py
@@ -10,9 +10,9 @@ from collections import defaultdict
 from contextlib import closing
 from functools import partial
 from qt.core import (
-    QAbstractItemView, QApplication, QCheckBox, QDialog, QDialogButtonBox,
-    QFormLayout, QGridLayout, QHBoxLayout, QIcon, QLabel, QLineEdit, QListWidget,
-    QListWidgetItem, QScrollArea, QSize, Qt, QToolButton, QVBoxLayout, QWidget
+    QAbstractItemView, QApplication, QCheckBox, QDialog, QDialogButtonBox, QFormLayout,
+    QGridLayout, QHBoxLayout, QIcon, QLabel, QLineEdit, QListWidget, QListWidgetItem,
+    QScrollArea, QSize, Qt, QToolButton, QVBoxLayout, QWidget,
 )
 from threading import Thread
 
@@ -20,7 +20,7 @@ from calibre import as_unicode
 from calibre.constants import ismacos
 from calibre.db.copy_to_library import copy_one_book
 from calibre.gui2 import (
-    Dispatcher, choose_dir, error_dialog, gprefs, info_dialog, warning_dialog
+    Dispatcher, choose_dir, error_dialog, gprefs, info_dialog, warning_dialog,
 )
 from calibre.gui2.actions import InterfaceAction
 from calibre.gui2.actions.choose_library import library_qicon
@@ -28,6 +28,7 @@ from calibre.gui2.dialogs.progress import ProgressDialog
 from calibre.gui2.widgets2 import Dialog
 from calibre.utils.config import prefs
 from calibre.utils.icu import numeric_sort_key, sort_key
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems, itervalues
 
 
diff --git a/src/calibre/gui2/actions/delete.py b/src/calibre/gui2/actions/delete.py
index c5783742fe..0f996c3f70 100644
--- a/src/calibre/gui2/actions/delete.py
+++ b/src/calibre/gui2/actions/delete.py
@@ -17,8 +17,9 @@ from calibre.gui2.actions import InterfaceAction
 from calibre.gui2.dialogs.confirm_delete import confirm
 from calibre.gui2.dialogs.confirm_delete_location import confirm_location
 from calibre.gui2.dialogs.delete_matching_from_device import (
-    DeleteMatchingFromDeviceDialog
+    DeleteMatchingFromDeviceDialog,
 )
+from calibre.utils.localization import ngettext
 from calibre.utils.recycle_bin import can_recycle
 
 single_shot = partial(QTimer.singleShot, 10)
diff --git a/src/calibre/gui2/actions/edit_metadata.py b/src/calibre/gui2/actions/edit_metadata.py
index e0216c909b..a2bdd1fa69 100644
--- a/src/calibre/gui2/actions/edit_metadata.py
+++ b/src/calibre/gui2/actions/edit_metadata.py
@@ -8,12 +8,11 @@ __docformat__ = 'restructuredtext en'
 import copy
 import os
 import shutil
-from functools import partial
 from contextlib import contextmanager
+from functools import partial
 from io import BytesIO
 from qt.core import (
-    QAction, QApplication, QDialog, QIcon, QMenu, QMimeData, QModelIndex, QTimer,
-    QUrl
+    QAction, QApplication, QDialog, QIcon, QMenu, QMimeData, QModelIndex, QTimer, QUrl,
 )
 
 from calibre.db.errors import NoSuchFormat
@@ -31,6 +30,7 @@ from calibre.library.comments import merge_comments
 from calibre.utils.config import tweaks
 from calibre.utils.date import is_date_undefined
 from calibre.utils.icu import sort_key
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems
 
 
diff --git a/src/calibre/gui2/actions/embed.py b/src/calibre/gui2/actions/embed.py
index c06e1a43d6..83beb2569c 100644
--- a/src/calibre/gui2/actions/embed.py
+++ b/src/calibre/gui2/actions/embed.py
@@ -5,12 +5,12 @@ __license__ = 'GPL v3'
 __copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'
 
 from functools import partial
-
-from qt.core import QTimer, QProgressDialog, Qt
+from qt.core import QProgressDialog, Qt, QTimer
 
 from calibre import force_unicode
 from calibre.gui2 import gprefs
 from calibre.gui2.actions import InterfaceAction
+from calibre.utils.localization import ngettext
 
 
 class EmbedAction(InterfaceAction):
diff --git a/src/calibre/gui2/actions/polish.py b/src/calibre/gui2/actions/polish.py
index c79c17a321..944978339f 100644
--- a/src/calibre/gui2/actions/polish.py
+++ b/src/calibre/gui2/actions/polish.py
@@ -5,22 +5,26 @@ __license__   = 'GPL v3'
 __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-import os, weakref, shutil, textwrap
+import os
+import shutil
+import textwrap
+import weakref
 from collections import OrderedDict
 from functools import partial
-from polyglot.builtins import iteritems, itervalues
+from qt.core import (
+    QApplication, QCheckBox, QDialog, QDialogButtonBox, QFrame, QGridLayout, QIcon,
+    QInputDialog, QLabel, QMenu, QModelIndex, QSize, QSizePolicy, QSpacerItem, Qt,
+    QTextEdit, QTimer,
+)
 
-from qt.core import (QDialog, QGridLayout, QIcon, QCheckBox, QLabel, QFrame,
-                      QApplication, QDialogButtonBox, Qt, QSize, QSpacerItem,
-                      QSizePolicy, QTimer, QModelIndex, QTextEdit,
-                      QInputDialog, QMenu)
-
-from calibre.gui2 import error_dialog, Dispatcher, gprefs, question_dialog
+from calibre.gui2 import Dispatcher, error_dialog, gprefs, question_dialog
 from calibre.gui2.actions import InterfaceAction
 from calibre.gui2.convert.metadata import create_opf_file
 from calibre.gui2.dialogs.progress import ProgressDialog
 from calibre.ptempfile import PersistentTemporaryDirectory
 from calibre.utils.config_base import tweaks
+from calibre.utils.localization import ngettext
+from polyglot.builtins import iteritems, itervalues
 
 
 class Polish(QDialog):  # {{{
diff --git a/src/calibre/gui2/actions/tag_mapper.py b/src/calibre/gui2/actions/tag_mapper.py
index 83c9ccc402..4ad0b5bb90 100644
--- a/src/calibre/gui2/actions/tag_mapper.py
+++ b/src/calibre/gui2/actions/tag_mapper.py
@@ -1,12 +1,12 @@
 #!/usr/bin/env python
 # License: GPLv3 Copyright: 2015, Kovid Goyal <kovid at kovidgoyal.net>
 
-
 from qt.core import QDialog
-from polyglot.builtins import iteritems
 
 from calibre.gui2 import gprefs
 from calibre.gui2.actions import InterfaceAction
+from calibre.utils.localization import ngettext
+from polyglot.builtins import iteritems
 
 
 class TagMapAction(InterfaceAction):
diff --git a/src/calibre/gui2/add.py b/src/calibre/gui2/add.py
index b91351c02b..dcac357d41 100644
--- a/src/calibre/gui2/add.py
+++ b/src/calibre/gui2/add.py
@@ -33,6 +33,7 @@ from calibre.utils.config import prefs
 from calibre.utils.filenames import make_long_path_useable
 from calibre.utils.icu import lower as icu_lower
 from calibre.utils.ipc.pool import Failure, Pool
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems, string_or_bytes
 from polyglot.queue import Empty
 
diff --git a/src/calibre/gui2/convert/bulk.py b/src/calibre/gui2/convert/bulk.py
index ab187c8805..cfd2c97405 100644
--- a/src/calibre/gui2/convert/bulk.py
+++ b/src/calibre/gui2/convert/bulk.py
@@ -3,20 +3,22 @@ __copyright__ = '2009, John Schember <john@nachtimwald.com>'
 __docformat__ = 'restructuredtext en'
 
 import shutil
+from qt.core import QDialog, QDialogButtonBox, QModelIndex
 
-from qt.core import QModelIndex, QDialog, QDialogButtonBox
-
-from calibre.gui2.convert.single import Config, GroupModel, gprefs
-from calibre.gui2.convert.look_and_feel import LookAndFeelWidget
+from calibre.ebooks.conversion.config import (
+    get_output_formats, sort_formats_by_preference,
+)
+from calibre.ebooks.conversion.plumber import Plumber
+from calibre.gui2.convert import GuiRecommendations
 from calibre.gui2.convert.heuristics import HeuristicsWidget
-from calibre.gui2.convert.search_and_replace import SearchAndReplaceWidget
+from calibre.gui2.convert.look_and_feel import LookAndFeelWidget
 from calibre.gui2.convert.page_setup import PageSetupWidget
+from calibre.gui2.convert.search_and_replace import SearchAndReplaceWidget
+from calibre.gui2.convert.single import Config, GroupModel, gprefs
 from calibre.gui2.convert.structure_detection import StructureDetectionWidget
 from calibre.gui2.convert.toc import TOCWidget
-from calibre.gui2.convert import GuiRecommendations
-from calibre.ebooks.conversion.plumber import Plumber
-from calibre.ebooks.conversion.config import sort_formats_by_preference, get_output_formats
 from calibre.utils.config import prefs
+from calibre.utils.localization import ngettext
 from calibre.utils.logging import Log
 
 
diff --git a/src/calibre/gui2/device.py b/src/calibre/gui2/device.py
index 09e7cce924..a9da487129 100644
--- a/src/calibre/gui2/device.py
+++ b/src/calibre/gui2/device.py
@@ -1,41 +1,56 @@
 __license__   = 'GPL v3'
 __copyright__ = '2008, Kovid Goyal <kovid at kovidgoyal.net>'
 
+import io
+
 # Imports {{{
-import os, traceback, time, io, re, sys, weakref
-from threading import Thread, Event
-
+import os
+import re
+import sys
+import time
+import traceback
+import weakref
 from qt.core import (
-    QMenu, QAction, QActionGroup, QIcon, pyqtSignal, QDialog,
-    QObject, QVBoxLayout, QDialogButtonBox, QCoreApplication,
-    QEventLoop, QTimer)
+    QAction, QActionGroup, QCoreApplication, QDialog, QDialogButtonBox, QEventLoop,
+    QIcon, QMenu, QObject, QTimer, QVBoxLayout, pyqtSignal,
+)
+from threading import Event, Thread
 
-from calibre.customize.ui import (available_input_formats, available_output_formats,
-    device_plugins, disabled_device_plugins)
-from calibre.devices.interface import DevicePlugin, currently_connected_device
-from calibre.devices.errors import (UserFeedback, OpenFeedback, OpenFailed, OpenActionNeeded,
-                                    InitialConnectionError)
-from calibre.ebooks.covers import cprefs, override_prefs, scale_cover, generate_cover
-from calibre.gui2.dialogs.choose_format_device import ChooseFormatDeviceDialog
-from calibre.utils.ipc.job import BaseJob
-from calibre.devices.scanner import DeviceScanner
-from calibre.gui2 import (config, error_dialog, Dispatcher, dynamic,
-        warning_dialog, info_dialog, choose_dir, FunctionDispatcher,
-        show_restart_warning, gprefs, question_dialog)
-from calibre.gui2.widgets import BusyCursor
-from calibre.ebooks.metadata import authors_to_string
-from calibre import preferred_encoding, prints, force_unicode, as_unicode, sanitize_file_name
-from calibre.utils.filenames import ascii_filename
-from calibre.devices.errors import (FreeSpaceError, WrongDestinationError,
-        BlacklistedDevice)
-from calibre.devices.folder_device.driver import FOLDER_DEVICE
+from calibre import (
+    as_unicode, force_unicode, preferred_encoding, prints, sanitize_file_name,
+)
 from calibre.constants import DEBUG
-from calibre.utils.config import tweaks, device_prefs
-from calibre.utils.img import scale_image
+from calibre.customize.ui import (
+    available_input_formats, available_output_formats, device_plugins,
+    disabled_device_plugins,
+)
+from calibre.devices.errors import (
+    BlacklistedDevice, FreeSpaceError, InitialConnectionError, OpenActionNeeded,
+    OpenFailed, OpenFeedback, UserFeedback, WrongDestinationError,
+)
+from calibre.devices.folder_device.driver import FOLDER_DEVICE
+from calibre.devices.interface import DevicePlugin, currently_connected_device
+from calibre.devices.scanner import DeviceScanner
+from calibre.ebooks.covers import cprefs, generate_cover, override_prefs, scale_cover
+from calibre.ebooks.metadata import authors_to_string
+from calibre.gui2 import (
+    Dispatcher, FunctionDispatcher, choose_dir, config, dynamic, error_dialog, gprefs,
+    info_dialog, question_dialog, show_restart_warning, warning_dialog,
+)
+from calibre.gui2.dialogs.choose_format_device import ChooseFormatDeviceDialog
+from calibre.gui2.widgets import BusyCursor
 from calibre.library.save_to_disk import find_plugboard
-from calibre.ptempfile import PersistentTemporaryFile, force_unicode as filename_to_unicode
-from polyglot.builtins import string_or_unicode
+from calibre.ptempfile import (
+    PersistentTemporaryFile, force_unicode as filename_to_unicode,
+)
+from calibre.utils.config import device_prefs, tweaks
+from calibre.utils.filenames import ascii_filename
+from calibre.utils.img import scale_image
+from calibre.utils.ipc.job import BaseJob
+from calibre.utils.localization import ngettext
 from polyglot import queue
+from polyglot.builtins import string_or_unicode
+
 # }}}
 
 
diff --git a/src/calibre/gui2/dialogs/duplicates.py b/src/calibre/gui2/dialogs/duplicates.py
index b7f460574c..74815ea069 100644
--- a/src/calibre/gui2/dialogs/duplicates.py
+++ b/src/calibre/gui2/dialogs/duplicates.py
@@ -6,14 +6,15 @@ __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
 import os.path
-
 from qt.core import (
-    QDialog, QGridLayout, QIcon, QLabel, QTreeWidget, QTreeWidgetItem, Qt,
-    QFont, QDialogButtonBox, QApplication)
+    QApplication, QDialog, QDialogButtonBox, QFont, QGridLayout, QIcon, QLabel, Qt,
+    QTreeWidget, QTreeWidgetItem,
+)
 
-from calibre.gui2 import gprefs
 from calibre.ebooks.metadata import authors_to_string
+from calibre.gui2 import gprefs
 from calibre.utils.icu import primary_sort_key
+from calibre.utils.localization import ngettext
 
 
 class DuplicatesQuestion(QDialog):
diff --git a/src/calibre/gui2/dialogs/match_books.py b/src/calibre/gui2/dialogs/match_books.py
index 7412b1f600..790bf50a15 100644
--- a/src/calibre/gui2/dialogs/match_books.py
+++ b/src/calibre/gui2/dialogs/match_books.py
@@ -6,12 +6,14 @@ __copyright__ = '2013, Kovid Goyal kovid@kovidgoyal.net'
 __docformat__ = 'restructuredtext en'
 
 
-from qt.core import (Qt, QDialog, QAbstractItemView, QTableWidgetItem,
-                      QApplication, QCursor, QTimer)
+from qt.core import (
+    QAbstractItemView, QApplication, QCursor, QDialog, Qt, QTableWidgetItem, QTimer,
+)
 
-from calibre.gui2 import gprefs, error_dialog
+from calibre.gui2 import error_dialog, gprefs
 from calibre.gui2.dialogs.match_books_ui import Ui_MatchBooks
 from calibre.utils.icu import sort_key
+from calibre.utils.localization import ngettext
 
 
 class TableItem(QTableWidgetItem):
diff --git a/src/calibre/gui2/dialogs/message_box.py b/src/calibre/gui2/dialogs/message_box.py
index 0e7b1b7560..f286e257a7 100644
--- a/src/calibre/gui2/dialogs/message_box.py
+++ b/src/calibre/gui2/dialogs/message_box.py
@@ -9,11 +9,12 @@ import sys
 from qt.core import (
     QAction, QApplication, QCheckBox, QDialog, QDialogButtonBox, QGridLayout, QIcon,
     QKeySequence, QLabel, QPainter, QPlainTextEdit, QSize, QSizePolicy, Qt,
-    QTextBrowser, QTextDocument, QVBoxLayout, QWidget, pyqtSignal
+    QTextBrowser, QTextDocument, QVBoxLayout, QWidget, pyqtSignal,
 )
 
 from calibre.constants import __version__, isfrozen
 from calibre.gui2 import gprefs
+from calibre.utils.localization import ngettext
 
 
 class Icon(QWidget):
@@ -491,8 +492,8 @@ class JobError(QDialog):  # {{{
 
 
 if __name__ == '__main__':
-    from calibre.gui2 import Application, question_dialog
     from calibre import prepare_string_for_xml
+    from calibre.gui2 import Application, question_dialog
     app = Application([])
     merged = {'Kovid Goyal': ['Waterloo', 'Doomed'], 'Someone Else': ['Some other book ' * 1000]}
     lines = []
diff --git a/src/calibre/gui2/dialogs/metadata_bulk.py b/src/calibre/gui2/dialogs/metadata_bulk.py
index 1ff57fbd65..a5c975db55 100644
--- a/src/calibre/gui2/dialogs/metadata_bulk.py
+++ b/src/calibre/gui2/dialogs/metadata_bulk.py
@@ -33,6 +33,7 @@ from calibre.utils.date import internal_iso_format_string, qt_to_dt
 from calibre.utils.icu import (
     capitalize, lower as icu_lower, sort_key, upper as icu_upper,
 )
+from calibre.utils.localization import ngettext
 from calibre.utils.titlecase import titlecase
 from polyglot.builtins import error_message, iteritems, itervalues, native_string_type
 
diff --git a/src/calibre/gui2/dialogs/template_dialog.py b/src/calibre/gui2/dialogs/template_dialog.py
index 96e73e0be6..e8bd1851c7 100644
--- a/src/calibre/gui2/dialogs/template_dialog.py
+++ b/src/calibre/gui2/dialogs/template_dialog.py
@@ -15,7 +15,7 @@ from qt.core import (
     QAbstractItemView, QApplication, QColor, QComboBox, QCursor, QDialog,
     QDialogButtonBox, QFont, QFontDatabase, QFontInfo, QFontMetrics, QIcon, QLineEdit,
     QPalette, QSize, QSyntaxHighlighter, Qt, QTableWidget, QTableWidgetItem,
-    QTextCharFormat, QTextOption, QVBoxLayout, pyqtSignal
+    QTextCharFormat, QTextOption, QVBoxLayout, pyqtSignal,
 )
 
 from calibre import sanitize_file_name
@@ -33,7 +33,7 @@ from calibre.utils.date import DEFAULT_DATE
 from calibre.utils.formatter import PythonTemplateContext, StopException
 from calibre.utils.formatter_functions import StoredObjectType, formatter_functions
 from calibre.utils.icu import lower as icu_lower, sort_key
-from calibre.utils.localization import localize_user_manual_link
+from calibre.utils.localization import localize_user_manual_link, ngettext
 from calibre.utils.resources import get_path as P
 
 
@@ -339,7 +339,7 @@ class TemplateDialog(QDialog, Ui_TemplateDialog):
             QDialog.__init__(self, parent, flags=Qt.WindowType.Dialog)
         else:
             QDialog.__init__(self, None, flags=Qt.WindowType.Window)
-            self.raise_() # Not needed on windows but here just in case
+            self.raise_()  # Not needed on windows but here just in case
         Ui_TemplateDialog.__init__(self)
         self.setupUi(self)
         self.setWindowIcon(self.windowIcon())
diff --git a/src/calibre/gui2/fts/search.py b/src/calibre/gui2/fts/search.py
index 5b5160a3b6..88cc891a50 100644
--- a/src/calibre/gui2/fts/search.py
+++ b/src/calibre/gui2/fts/search.py
@@ -11,10 +11,9 @@ from contextlib import suppress
 from functools import partial
 from itertools import count
 from qt.core import (
-    QAbstractItemModel, QAbstractItemView, QCheckBox, QDialog, QDialogButtonBox,
-    QFont, QHBoxLayout, QIcon, QLabel, QMenu, QModelIndex, QPixmap, QPushButton,
-    QRect, QSize, QSplitter, QStackedWidget, Qt, QTreeView, QVBoxLayout, QWidget,
-    pyqtSignal
+    QAbstractItemModel, QAbstractItemView, QCheckBox, QDialog, QDialogButtonBox, QFont,
+    QHBoxLayout, QIcon, QLabel, QMenu, QModelIndex, QPixmap, QPushButton, QRect, QSize,
+    QSplitter, QStackedWidget, Qt, QTreeView, QVBoxLayout, QWidget, pyqtSignal,
 )
 from threading import Event, Thread
 
@@ -22,7 +21,7 @@ from calibre import fit_image, prepare_string_for_xml
 from calibre.db import FTSQueryError
 from calibre.ebooks.metadata import authors_to_string, fmt_sidx
 from calibre.gui2 import (
-    config, error_dialog, gprefs, info_dialog, question_dialog, safe_open_url
+    config, error_dialog, gprefs, info_dialog, question_dialog, safe_open_url,
 )
 from calibre.gui2.fts.utils import get_db
 from calibre.gui2.library.models import render_pin
@@ -31,6 +30,7 @@ from calibre.gui2.ui import get_gui
 from calibre.gui2.viewer.widgets import ResultsDelegate, SearchBox
 from calibre.gui2.widgets import BusyCursor
 from calibre.gui2.widgets2 import HTMLDisplay
+from calibre.utils.localization import ngettext
 
 ROOT = QModelIndex()
 sanitize_text_pat = re.compile(r'\s+')
diff --git a/src/calibre/gui2/init.py b/src/calibre/gui2/init.py
index c1b8484f80..5b31623aea 100644
--- a/src/calibre/gui2/init.py
+++ b/src/calibre/gui2/init.py
@@ -7,15 +7,15 @@ __docformat__ = 'restructuredtext en'
 
 import functools
 from qt.core import (
-    QAction, QApplication, QDialog, QEvent, QIcon, QLabel, QMenu, QPixmap, QUrl,
-    QSizePolicy, QStackedWidget, QStatusBar, QStyle, QStyleOption, QSplitter,
-    QStylePainter, Qt, QTabBar, QTimer, QToolButton, QVBoxLayout, QWidget
+    QAction, QApplication, QDialog, QEvent, QIcon, QLabel, QMenu, QPixmap, QSizePolicy,
+    QSplitter, QStackedWidget, QStatusBar, QStyle, QStyleOption, QStylePainter, Qt,
+    QTabBar, QTimer, QToolButton, QUrl, QVBoxLayout, QWidget,
 )
 
 from calibre.constants import get_appname_for_display, get_version, ismacos
 from calibre.customize.ui import find_plugin
 from calibre.gui2 import (
-    config, error_dialog, gprefs, is_widescreen, open_local_file, open_url
+    config, error_dialog, gprefs, is_widescreen, open_local_file, open_url,
 )
 from calibre.gui2.book_details import BookDetails
 from calibre.gui2.layout_menu import LayoutMenu
@@ -26,7 +26,7 @@ from calibre.gui2.tag_browser.ui import TagBrowserWidget
 from calibre.gui2.widgets import LayoutButton, Splitter
 from calibre.utils.config import prefs
 from calibre.utils.icu import sort_key
-from calibre.utils.localization import localize_website_link
+from calibre.utils.localization import localize_website_link, ngettext
 
 _keep_refs = []
 
diff --git a/src/calibre/gui2/jobs.py b/src/calibre/gui2/jobs.py
index 52e1321632..700f24475c 100644
--- a/src/calibre/gui2/jobs.py
+++ b/src/calibre/gui2/jobs.py
@@ -10,28 +10,28 @@ Job management.
 '''
 
 import time
+from qt.core import (
+    QAbstractItemDelegate, QAbstractTableModel, QAction, QApplication, QByteArray,
+    QCoreApplication, QDialog, QDialogButtonBox, QEvent, QHBoxLayout, QIcon,
+    QItemSelectionModel, QLabel, QModelIndex, QPlainTextEdit, QSize, QSizePolicy,
+    QSortFilterProxyModel, QStyle, QStyleOption, QStyleOptionProgressBar, QStylePainter,
+    Qt, QTextBrowser, QTimer, QToolTip, QVBoxLayout, QWidget, pyqtSignal,
+)
 
-from qt.core import (QAbstractTableModel, QModelIndex, Qt, QStylePainter,
-    QTimer, pyqtSignal, QIcon, QDialog, QAbstractItemDelegate, QApplication, QEvent,
-    QSize, QStyleOptionProgressBar, QStyle, QToolTip, QWidget, QStyleOption,
-    QHBoxLayout, QVBoxLayout, QSizePolicy, QLabel, QCoreApplication, QAction, QItemSelectionModel,
-    QByteArray, QSortFilterProxyModel, QTextBrowser, QPlainTextEdit, QDialogButtonBox)
-
-from calibre import strftime
-from calibre.constants import islinux, isbsd
-from calibre.utils.ipc.server import Server
-from calibre.utils.ipc.job import ParallelJob
-from calibre.gui2 import (Dispatcher, error_dialog, question_dialog,
-        config, gprefs)
+from calibre import __appname__, as_unicode, strftime
+from calibre.constants import isbsd, islinux
+from calibre.db.utils import human_readable_interval
+from calibre.gui2 import Dispatcher, config, error_dialog, gprefs, question_dialog
 from calibre.gui2.device import DeviceJob
 from calibre.gui2.dialogs.jobs_ui import Ui_JobsDialog
-from calibre import __appname__, as_unicode
 from calibre.gui2.progress_indicator import ProgressIndicator
-from calibre.gui2.threaded_jobs import ThreadedJobServer, ThreadedJob
+from calibre.gui2.threaded_jobs import ThreadedJob, ThreadedJobServer
 from calibre.gui2.widgets2 import Dialog
-from calibre.utils.search_query_parser import SearchQueryParser, ParseException
-from calibre.db.utils import human_readable_interval
 from calibre.utils.icu import lower
+from calibre.utils.ipc.job import ParallelJob
+from calibre.utils.ipc.server import Server
+from calibre.utils.localization import ngettext
+from calibre.utils.search_query_parser import ParseException, SearchQueryParser
 from polyglot.queue import Empty, Queue
 
 
diff --git a/src/calibre/gui2/library/annotations.py b/src/calibre/gui2/library/annotations.py
index 17a2b7b776..60c36ab53d 100644
--- a/src/calibre/gui2/library/annotations.py
+++ b/src/calibre/gui2/library/annotations.py
@@ -7,28 +7,29 @@ import os
 import re
 from functools import lru_cache, partial
 from qt.core import (
-    QAbstractItemView, QApplication, QCheckBox, QComboBox, QDateTime,
-    QDialog, QDialogButtonBox, QFont, QFormLayout, QFrame, QHBoxLayout, QIcon,
-    QKeySequence, QLabel, QLocale, QMenu, QPalette, QPlainTextEdit, QSize, QSplitter,
-    Qt, QTextBrowser, QTimer, QToolButton, QTreeWidget, QTreeWidgetItem, QVBoxLayout,
-    QWidget, pyqtSignal
+    QAbstractItemView, QApplication, QCheckBox, QComboBox, QDateTime, QDialog,
+    QDialogButtonBox, QFont, QFormLayout, QFrame, QHBoxLayout, QIcon, QKeySequence,
+    QLabel, QLocale, QMenu, QPalette, QPlainTextEdit, QSize, QSplitter, Qt,
+    QTextBrowser, QTimer, QToolButton, QTreeWidget, QTreeWidgetItem, QVBoxLayout,
+    QWidget, pyqtSignal,
 )
 from urllib.parse import quote
 
 from calibre import prepare_string_for_xml
 from calibre.constants import (
-    builtin_colors_dark, builtin_colors_light, builtin_decorations
+    builtin_colors_dark, builtin_colors_light, builtin_decorations,
 )
 from calibre.db.backend import FTSQueryError
 from calibre.ebooks.metadata import authors_to_string, fmt_sidx
 from calibre.gui2 import (
     Application, choose_save_file, config, error_dialog, gprefs, is_dark_theme,
-    safe_open_url
+    safe_open_url,
 )
 from calibre.gui2.dialogs.confirm_delete import confirm
 from calibre.gui2.viewer.widgets import ResultsDelegate, SearchBox
 from calibre.gui2.widgets import BusyCursor
 from calibre.gui2.widgets2 import Dialog, RightClickButton
+from calibre.utils.localization import ngettext
 
 
 def render_timestamp(ts):
diff --git a/src/calibre/gui2/library/models.py b/src/calibre/gui2/library/models.py
index 30e9c1755b..96772474fc 100644
--- a/src/calibre/gui2/library/models.py
+++ b/src/calibre/gui2/library/models.py
@@ -38,7 +38,7 @@ from calibre.utils.date import (
     UNDEFINED_DATE, as_local_time, dt_factory, is_date_undefined, qt_to_dt,
 )
 from calibre.utils.icu import sort_key
-from calibre.utils.localization import calibre_langcode_to_name
+from calibre.utils.localization import calibre_langcode_to_name, ngettext
 from calibre.utils.resources import get_path as P
 from calibre.utils.search_query_parser import ParseException, SearchQueryParser
 from polyglot.builtins import iteritems, itervalues, string_or_bytes
diff --git a/src/calibre/gui2/metadata/basic_widgets.py b/src/calibre/gui2/metadata/basic_widgets.py
index 16ba3210b6..8e83ee72ad 100644
--- a/src/calibre/gui2/metadata/basic_widgets.py
+++ b/src/calibre/gui2/metadata/basic_widgets.py
@@ -12,10 +12,11 @@ import textwrap
 import weakref
 from datetime import date, datetime
 from qt.core import (
-    QAction, QApplication, QDateTime, QDialog, QDialogButtonBox, QDoubleSpinBox, QAbstractItemView,
-    QGridLayout, QIcon, QKeySequence, QLabel, QLineEdit, QListWidgetItem, QMenu,
-    QMessageBox, QPixmap, QPlainTextEdit, QSize, QSizePolicy, Qt, QToolButton, QComboBox,
-    QUndoCommand, QUndoStack, QUrl, QVBoxLayout, QWidget, pyqtSignal
+    QAbstractItemView, QAction, QApplication, QComboBox, QDateTime, QDialog,
+    QDialogButtonBox, QDoubleSpinBox, QGridLayout, QIcon, QKeySequence, QLabel,
+    QLineEdit, QListWidgetItem, QMenu, QMessageBox, QPixmap, QPlainTextEdit, QSize,
+    QSizePolicy, Qt, QToolButton, QUndoCommand, QUndoStack, QUrl, QVBoxLayout, QWidget,
+    pyqtSignal,
 )
 
 from calibre import strftime
@@ -24,12 +25,13 @@ from calibre.customize.ui import run_plugins_on_import
 from calibre.db import SPOOL_SIZE
 from calibre.ebooks import BOOK_EXTENSIONS
 from calibre.ebooks.metadata import (
-    authors_to_sort_string, check_isbn, string_to_authors, title_sort
+    authors_to_sort_string, check_isbn, string_to_authors, title_sort,
 )
 from calibre.ebooks.metadata.meta import get_metadata
 from calibre.ebooks.oeb.polish.main import SUPPORTED as EDIT_SUPPORTED
 from calibre.gui2 import (
-    choose_files_and_remember_all_files, choose_images, error_dialog, file_icon_provider, gprefs
+    choose_files_and_remember_all_files, choose_images, error_dialog,
+    file_icon_provider, gprefs,
 )
 from calibre.gui2.comments_editor import Editor
 from calibre.gui2.complete2 import EditWithComplete
@@ -38,17 +40,18 @@ from calibre.gui2.languages import LanguagesEdit as LE
 from calibre.gui2.widgets import EnLineEdit, FormatList as _FormatList, ImageView
 from calibre.gui2.widgets2 import (
     DateTimeEdit, Dialog, RatingEditor, RightClickButton, access_key,
-    populate_standard_spinbox_context_menu
+    populate_standard_spinbox_context_menu,
 )
 from calibre.library.comments import comments_to_html
 from calibre.ptempfile import PersistentTemporaryFile, SpooledTemporaryFile
 from calibre.utils.config import prefs, tweaks
 from calibre.utils.date import (
     UNDEFINED_DATE, as_local_time, internal_iso_format_string, is_date_undefined,
-    local_tz, parse_only_date, qt_to_dt, utcfromtimestamp
+    local_tz, parse_only_date, qt_to_dt, utcfromtimestamp,
 )
 from calibre.utils.filenames import make_long_path_useable
 from calibre.utils.icu import sort_key, strcmp
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems
 
 
@@ -1221,7 +1224,7 @@ class Cover(ImageView):  # {{{
         if not cdata:
             return
         from calibre.utils.img import (
-            image_from_data, image_to_data, remove_borders_from_image
+            image_from_data, image_to_data, remove_borders_from_image,
         )
         img = image_from_data(cdata)
         nimg = remove_borders_from_image(img)
diff --git a/src/calibre/gui2/metadata/bulk_download.py b/src/calibre/gui2/metadata/bulk_download.py
index 95296cb58a..03cbeed404 100644
--- a/src/calibre/gui2/metadata/bulk_download.py
+++ b/src/calibre/gui2/metadata/bulk_download.py
@@ -5,17 +5,17 @@ __license__   = 'GPL v3'
 __copyright__ = '2011, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-import os, time, shutil
+import os
+import shutil
+import time
+from qt.core import QDialog, QDialogButtonBox, QGridLayout, QIcon, QLabel, Qt
 from threading import Thread
 
-from qt.core import (QIcon, QDialog,
-        QDialogButtonBox, QLabel, QGridLayout, Qt)
-
-from calibre.gui2.threaded_jobs import ThreadedJob
 from calibre.ebooks.metadata.opf2 import metadata_to_opf
-from calibre.utils.ipc.simple_worker import fork_job, WorkerError
-from calibre.ptempfile import (PersistentTemporaryDirectory,
-        PersistentTemporaryFile)
+from calibre.gui2.threaded_jobs import ThreadedJob
+from calibre.ptempfile import PersistentTemporaryDirectory, PersistentTemporaryFile
+from calibre.utils.ipc.simple_worker import WorkerError, fork_job
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems
 
 # Start download {{{
diff --git a/src/calibre/gui2/metadata/diff.py b/src/calibre/gui2/metadata/diff.py
index e12e283b5e..4266ba1239 100644
--- a/src/calibre/gui2/metadata/diff.py
+++ b/src/calibre/gui2/metadata/diff.py
@@ -27,6 +27,7 @@ from calibre.gui2.widgets2 import RightClickButton
 from calibre.ptempfile import PersistentTemporaryFile
 from calibre.utils.date import UNDEFINED_DATE
 from calibre.utils.icu import lower as icu_lower
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems, itervalues
 
 Widgets = namedtuple('Widgets', 'new old label button')
diff --git a/src/calibre/gui2/metadata/single.py b/src/calibre/gui2/metadata/single.py
index 2dffa514f0..d8cb7334c6 100644
--- a/src/calibre/gui2/metadata/single.py
+++ b/src/calibre/gui2/metadata/single.py
@@ -32,7 +32,7 @@ from calibre.gui2.metadata.single_download import FullFetch
 from calibre.gui2.widgets2 import CenteredToolButton
 from calibre.library.comments import merge_comments as merge_two_comments
 from calibre.utils.date import local_tz
-from calibre.utils.localization import canonicalize_lang
+from calibre.utils.localization import canonicalize_lang, ngettext
 from polyglot.builtins import iteritems
 
 BASE_TITLE = _('Edit metadata')
diff --git a/src/calibre/gui2/preferences/coloring.py b/src/calibre/gui2/preferences/coloring.py
index a1df13c6c0..76544c7a35 100644
--- a/src/calibre/gui2/preferences/coloring.py
+++ b/src/calibre/gui2/preferences/coloring.py
@@ -10,30 +10,29 @@ import os
 import textwrap
 from functools import partial
 from qt.core import (
-    QAbstractItemView, QAbstractListModel, QApplication, QCheckBox, QComboBox,
-    QDialog, QDialogButtonBox, QDoubleValidator, QFrame, QGridLayout, QIcon,
-    QIntValidator, QItemSelectionModel, QLabel, QLineEdit, QListView,
-    QPalette, QPushButton, QScrollArea, QSize, QSizePolicy, QSpacerItem,
-    QStandardItem, QStandardItemModel, Qt, QToolButton, QVBoxLayout, QWidget,
-    QItemSelection, QListWidget, QListWidgetItem, pyqtSignal
+    QAbstractItemView, QAbstractListModel, QApplication, QCheckBox, QComboBox, QDialog,
+    QDialogButtonBox, QDoubleValidator, QFrame, QGridLayout, QIcon, QIntValidator,
+    QItemSelection, QItemSelectionModel, QLabel, QLineEdit, QListView, QListWidget,
+    QListWidgetItem, QPalette, QPushButton, QScrollArea, QSize, QSizePolicy,
+    QSpacerItem, QStandardItem, QStandardItemModel, Qt, QToolButton, QVBoxLayout,
+    QWidget, pyqtSignal,
 )
 
 from calibre import as_unicode, prepare_string_for_xml, sanitize_file_name
 from calibre.constants import config_dir
 from calibre.gui2 import (
     choose_files, choose_save_file, error_dialog, gprefs, open_local_file,
-    pixmap_to_data, question_dialog
+    pixmap_to_data, question_dialog,
 )
 from calibre.gui2.dialogs.template_dialog import TemplateDialog
 from calibre.gui2.metadata.single_download import RichTextDelegate
 from calibre.gui2.preferences import ListViewWithMoveByKeyPress
 from calibre.gui2.widgets2 import ColorButton, FlowLayout, Separator
 from calibre.library.coloring import (
-    Rule, color_row_key, conditionable_columns, displayable_columns,
-    rule_from_template
+    Rule, color_row_key, conditionable_columns, displayable_columns, rule_from_template,
 )
 from calibre.utils.icu import lower, sort_key
-from calibre.utils.localization import lang_map
+from calibre.utils.localization import lang_map, ngettext
 from polyglot.builtins import iteritems
 
 all_columns_string = _('All columns')
diff --git a/src/calibre/gui2/preferences/create_custom_column.py b/src/calibre/gui2/preferences/create_custom_column.py
index 9f6e4c6602..aa3a83ea50 100644
--- a/src/calibre/gui2/preferences/create_custom_column.py
+++ b/src/calibre/gui2/preferences/create_custom_column.py
@@ -6,19 +6,20 @@ __copyright__ = '2010, Kovid Goyal <kovid at kovidgoyal.net>'
 
 '''Dialog to create a new custom column'''
 
-import copy, re
+import copy
+import re
 from enum import Enum
 from functools import partial
-
 from qt.core import (
-    QDialog, Qt, QColor, QIcon, QVBoxLayout, QLabel, QGridLayout,
-    QDialogButtonBox, QWidget, QLineEdit, QHBoxLayout, QComboBox,
-    QCheckBox, QSpinBox, QRadioButton, QGroupBox
+    QCheckBox, QColor, QComboBox, QDialog, QDialogButtonBox, QGridLayout, QGroupBox,
+    QHBoxLayout, QIcon, QLabel, QLineEdit, QRadioButton, QSpinBox, Qt, QVBoxLayout,
+    QWidget,
 )
 
 from calibre.gui2 import error_dialog
 from calibre.gui2.dialogs.template_line_editor import TemplateLineEditor
-from calibre.utils.date import parse_date, UNDEFINED_DATE
+from calibre.utils.date import UNDEFINED_DATE, parse_date
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems
 
 
diff --git a/src/calibre/gui2/preferences/metadata_sources.py b/src/calibre/gui2/preferences/metadata_sources.py
index 4bba974884..63f0354843 100644
--- a/src/calibre/gui2/preferences/metadata_sources.py
+++ b/src/calibre/gui2/preferences/metadata_sources.py
@@ -7,18 +7,19 @@ __docformat__ = 'restructuredtext en'
 
 from operator import attrgetter
 from qt.core import (
-    QAbstractListModel, QAbstractTableModel, QDialogButtonBox, QFrame, QIcon, QLabel,
-    QScrollArea, Qt, QVBoxLayout, QWidget, pyqtSignal, QDialog, QMenu, QCursor
+    QAbstractListModel, QAbstractTableModel, QCursor, QDialog, QDialogButtonBox, QFrame,
+    QIcon, QLabel, QMenu, QScrollArea, Qt, QVBoxLayout, QWidget, pyqtSignal,
 )
 
 from calibre.customize.ui import (
     all_metadata_plugins, default_disabled_plugins, disable_plugin, enable_plugin,
-    is_disabled
+    is_disabled,
 )
 from calibre.ebooks.metadata.sources.prefs import msprefs
 from calibre.gui2 import error_dialog, question_dialog
 from calibre.gui2.preferences import ConfigWidgetBase, test_widget
 from calibre.gui2.preferences.metadata_sources_ui import Ui_Form
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems
 
 
diff --git a/src/calibre/gui2/preferences/server.py b/src/calibre/gui2/preferences/server.py
index a49a9848fc..e7c10a8883 100644
--- a/src/calibre/gui2/preferences/server.py
+++ b/src/calibre/gui2/preferences/server.py
@@ -12,14 +12,14 @@ from qt.core import (
     QApplication, QCheckBox, QComboBox, QDialog, QDialogButtonBox, QDoubleSpinBox,
     QFormLayout, QFrame, QHBoxLayout, QIcon, QLabel, QLayout, QLineEdit, QListWidget,
     QPlainTextEdit, QPushButton, QScrollArea, QSize, QSizePolicy, QSpinBox, Qt,
-    QTabWidget, QTimer, QToolButton, QUrl, QVBoxLayout, QWidget, pyqtSignal, sip
+    QTabWidget, QTimer, QToolButton, QUrl, QVBoxLayout, QWidget, pyqtSignal, sip,
 )
 
 from calibre import as_unicode
 from calibre.constants import isportable, iswindows
 from calibre.gui2 import (
-    choose_files, choose_save_file, config, error_dialog, gprefs, info_dialog,
-    open_url, warning_dialog
+    choose_files, choose_save_file, config, error_dialog, gprefs, info_dialog, open_url,
+    warning_dialog,
 )
 from calibre.gui2.preferences import AbortCommit, ConfigWidgetBase, test_widget
 from calibre.gui2.widgets import HistoryLineEdit
@@ -29,9 +29,10 @@ from calibre.srv.library_broker import load_gui_libraries
 from calibre.srv.loop import parse_trusted_ips
 from calibre.srv.opts import change_settings, options, server_config
 from calibre.srv.users import (
-    UserManager, create_user_data, validate_password, validate_username
+    UserManager, create_user_data, validate_password, validate_username,
 )
 from calibre.utils.icu import primary_sort_key
+from calibre.utils.localization import ngettext
 from calibre.utils.shared_file import share_open
 from polyglot.builtins import as_bytes
 
diff --git a/src/calibre/gui2/search_restriction_mixin.py b/src/calibre/gui2/search_restriction_mixin.py
index f738601677..96f9f9eae7 100644
--- a/src/calibre/gui2/search_restriction_mixin.py
+++ b/src/calibre/gui2/search_restriction_mixin.py
@@ -8,14 +8,14 @@ from functools import partial
 from qt.core import (
     QAbstractItemView, QAction, QComboBox, QDialog, QDialogButtonBox, QFrame,
     QGridLayout, QIcon, QLabel, QLineEdit, QListView, QMenu, QRadioButton, QSize,
-    QStringListModel, Qt, QTextBrowser, QVBoxLayout, QSortFilterProxyModel
+    QSortFilterProxyModel, QStringListModel, Qt, QTextBrowser, QVBoxLayout,
 )
 
 from calibre.gui2 import error_dialog, gprefs, question_dialog
 from calibre.gui2.dialogs.confirm_delete import confirm
 from calibre.gui2.widgets import ComboBoxWithHelp
 from calibre.utils.icu import sort_key
-from calibre.utils.localization import localize_user_manual_link, pgettext
+from calibre.utils.localization import localize_user_manual_link, ngettext, pgettext
 from calibre.utils.search_query_parser import ParseException
 
 
diff --git a/src/calibre/gui2/tag_browser/ui.py b/src/calibre/gui2/tag_browser/ui.py
index bd7f07b26e..d4c67d2997 100644
--- a/src/calibre/gui2/tag_browser/ui.py
+++ b/src/calibre/gui2/tag_browser/ui.py
@@ -5,22 +5,25 @@ __license__   = 'GPL v3'
 __copyright__ = '2011, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-import copy, textwrap
+import copy
+import textwrap
 from functools import partial
-
 from qt.core import (
-    Qt, QIcon, QWidget, QHBoxLayout, QVBoxLayout, QToolButton, QLabel, QFrame, QDialog, QComboBox, QLineEdit,
-    QTimer, QMenu, QActionGroup, QAction, QSizePolicy, pyqtSignal)
+    QAction, QActionGroup, QComboBox, QDialog, QFrame, QHBoxLayout, QIcon, QLabel,
+    QLineEdit, QMenu, QSizePolicy, Qt, QTimer, QToolButton, QVBoxLayout, QWidget,
+    pyqtSignal,
+)
 
-from calibre.gui2 import error_dialog, question_dialog, gprefs, config
+from calibre.ebooks.metadata import title_sort
+from calibre.gui2 import config, error_dialog, gprefs, question_dialog
+from calibre.gui2.dialogs.edit_authors_dialog import EditAuthorsDialog
+from calibre.gui2.dialogs.tag_categories import TagCategories
+from calibre.gui2.dialogs.tag_list_editor import TagListEditor
+from calibre.gui2.tag_browser.view import TagsView
 from calibre.gui2.widgets import HistoryLineEdit
 from calibre.library.field_metadata import category_icon_map
 from calibre.utils.icu import sort_key
-from calibre.gui2.tag_browser.view import TagsView
-from calibre.ebooks.metadata import title_sort
-from calibre.gui2.dialogs.tag_categories import TagCategories
-from calibre.gui2.dialogs.tag_list_editor import TagListEditor
-from calibre.gui2.dialogs.edit_authors_dialog import EditAuthorsDialog
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems
 
 
diff --git a/src/calibre/gui2/tweak_book/boss.py b/src/calibre/gui2/tweak_book/boss.py
index 3785c83ec3..7958bef8eb 100644
--- a/src/calibre/gui2/tweak_book/boss.py
+++ b/src/calibre/gui2/tweak_book/boss.py
@@ -1,7 +1,6 @@
 #!/usr/bin/env python
 # License: GPLv3 Copyright: 2013, Kovid Goyal <kovid at kovidgoyal.net>
 
-
 import errno
 import os
 import shutil
@@ -11,39 +10,37 @@ from functools import partial, wraps
 from qt.core import (
     QApplication, QCheckBox, QDialog, QDialogButtonBox, QGridLayout, QIcon,
     QInputDialog, QLabel, QMimeData, QObject, QSize, Qt, QTimer, QUrl, QVBoxLayout,
-    pyqtSignal
+    pyqtSignal,
 )
 
 from calibre import isbytestring, prints
 from calibre.constants import cache_dir, iswindows
 from calibre.ebooks.oeb.base import urlnormalize
 from calibre.ebooks.oeb.polish.container import (
-    OEB_DOCS, OEB_STYLES, clone_container, get_container as _gc, guess_type
-)
-from calibre.ebooks.oeb.polish.cover import (
-    mark_as_cover, mark_as_titlepage, set_cover
+    OEB_DOCS, OEB_STYLES, clone_container, get_container as _gc, guess_type,
 )
+from calibre.ebooks.oeb.polish.cover import mark_as_cover, mark_as_titlepage, set_cover
 from calibre.ebooks.oeb.polish.css import filter_css, rename_class
 from calibre.ebooks.oeb.polish.main import SUPPORTED, tweak_polish
 from calibre.ebooks.oeb.polish.pretty import fix_all_html, pretty_all
 from calibre.ebooks.oeb.polish.replace import (
-    get_recommended_folders, rationalize_folders, rename_files, replace_file
+    get_recommended_folders, rationalize_folders, rename_files, replace_file,
 )
 from calibre.ebooks.oeb.polish.split import AbortError, merge, multisplit, split
 from calibre.ebooks.oeb.polish.toc import (
-    create_inline_toc, mark_as_nav, remove_names_from_toc
+    create_inline_toc, mark_as_nav, remove_names_from_toc,
 )
 from calibre.ebooks.oeb.polish.utils import (
-    link_stylesheets, setup_css_parser_serialization as scs
+    link_stylesheets, setup_css_parser_serialization as scs,
 )
 from calibre.gui2 import (
-    add_to_recent_docs, choose_dir, choose_files, choose_save_file, error_dialog, warning_dialog,
-    info_dialog, open_url, question_dialog
+    add_to_recent_docs, choose_dir, choose_files, choose_save_file, error_dialog,
+    info_dialog, open_url, question_dialog, warning_dialog,
 )
 from calibre.gui2.dialogs.confirm_delete import confirm
 from calibre.gui2.tweak_book import (
     actions, current_container, dictionaries, editor_name, editors, set_book_locale,
-    set_current_container, tprefs
+    set_current_container, tprefs,
 )
 from calibre.gui2.tweak_book.completion.worker import completion_worker
 from calibre.gui2.tweak_book.editor import editor_from_syntax, syntax_from_mime
@@ -52,23 +49,22 @@ from calibre.gui2.tweak_book.file_list import FILE_COPY_MIME, NewFileDialog
 from calibre.gui2.tweak_book.preferences import Preferences
 from calibre.gui2.tweak_book.preview import parse_worker
 from calibre.gui2.tweak_book.save import (
-    SaveManager, find_first_existing_ancestor, save_container
+    SaveManager, find_first_existing_ancestor, save_container,
 )
 from calibre.gui2.tweak_book.search import run_search, validate_search_request
-from calibre.gui2.tweak_book.spell import (
-    find_next as find_next_word, find_next_error
-)
+from calibre.gui2.tweak_book.spell import find_next as find_next_word, find_next_error
 from calibre.gui2.tweak_book.toc import TOCEditor
 from calibre.gui2.tweak_book.undo import GlobalUndoHistory
 from calibre.gui2.tweak_book.widgets import (
     AddCover, FilterCSS, ImportForeign, InsertLink, InsertSemantics, InsertTag,
-    MultiSplit, QuickOpen, RationalizeFolders
+    MultiSplit, QuickOpen, RationalizeFolders,
 )
 from calibre.gui2.widgets import BusyCursor
 from calibre.ptempfile import PersistentTemporaryDirectory, TemporaryDirectory
 from calibre.utils.config import JSONConfig
 from calibre.utils.icu import numeric_sort_key
 from calibre.utils.imghdr import identify
+from calibre.utils.localization import ngettext
 from calibre.utils.tdir_in_cache import tdir_in_cache
 from polyglot.builtins import as_bytes, iteritems, itervalues, string_or_bytes
 from polyglot.urllib import urlparse
@@ -216,7 +212,7 @@ class Boss(QObject):
                 ed.apply_settings(dictionaries_changed=p.dictionaries_changed)
         if orig_spell != tprefs['inline_spell_check']:
             from calibre.gui2.tweak_book.editor.syntax.html import (
-                refresh_spell_check_status
+                refresh_spell_check_status,
             )
             refresh_spell_check_status()
             for ed in itervalues(editors):
@@ -502,7 +498,7 @@ class Boss(QObject):
         added_name = self.do_add_file(d.file_name, d.file_data, using_template=d.using_template, edit_file=True)
         if d.file_name.rpartition('.')[2].lower() in ('ttf', 'otf', 'woff'):
             from calibre.gui2.tweak_book.manage_fonts import (
-                show_font_face_rule_for_font_file
+                show_font_face_rule_for_font_file,
             )
             show_font_face_rule_for_font_file(d.file_data, added_name, self.gui)
 
@@ -567,7 +563,7 @@ class Boss(QObject):
             completion_worker().clear_caches('names')
             if added_fonts:
                 from calibre.gui2.tweak_book.manage_fonts import (
-                    show_font_face_rule_for_font_files
+                    show_font_face_rule_for_font_files,
                 )
                 show_font_face_rule_for_font_files(c, added_fonts, self.gui)
 
@@ -1219,7 +1215,7 @@ class Boss(QObject):
 
     def editor_class_clicked(self, class_data):
         from calibre.gui2.tweak_book.jump_to_class import (
-            NoMatchingRuleFound, NoMatchingTagFound, find_first_matching_rule
+            NoMatchingRuleFound, NoMatchingTagFound, find_first_matching_rule,
         )
         ed = self.gui.central.current_editor
         name = editor_name(ed)
@@ -1617,7 +1613,7 @@ class Boss(QObject):
         if not self.ensure_book(_('You must first open a book in order to compress images.')):
             return
         from calibre.gui2.tweak_book.polish import (
-            CompressImages, CompressImagesProgress, show_report
+            CompressImages, CompressImagesProgress, show_report,
         )
         d = CompressImages(self.gui)
         if d.exec() == QDialog.DialogCode.Accepted:
diff --git a/src/calibre/gui2/tweak_book/check_links.py b/src/calibre/gui2/tweak_book/check_links.py
index 09e08d4bc3..02dca7da12 100644
--- a/src/calibre/gui2/tweak_book/check_links.py
+++ b/src/calibre/gui2/tweak_book/check_links.py
@@ -1,19 +1,20 @@
 #!/usr/bin/env python
 # License: GPLv3 Copyright: 2015, Kovid Goyal <kovid at kovidgoyal.net>
 
-
 from collections import defaultdict
+from qt.core import (
+    QCheckBox, QDialogButtonBox, QHBoxLayout, QIcon, QInputDialog, QLabel, QProgressBar,
+    QSizePolicy, QStackedWidget, Qt, QTextBrowser, QVBoxLayout, QWidget, pyqtSignal,
+)
 from threading import Thread
 
-from qt.core import (
-    QCheckBox, QHBoxLayout, QIcon, QInputDialog, QLabel, QProgressBar, QSizePolicy,
-    QStackedWidget, Qt, QTextBrowser, QVBoxLayout, QWidget, pyqtSignal, QDialogButtonBox
-)
-
 from calibre.gui2 import error_dialog
-from calibre.gui2.tweak_book import current_container, editors, set_current_container, tprefs
+from calibre.gui2.tweak_book import (
+    current_container, editors, set_current_container, tprefs,
+)
 from calibre.gui2.tweak_book.boss import get_boss
 from calibre.gui2.tweak_book.widgets import Dialog
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems
 
 
@@ -168,6 +169,7 @@ class CheckExternalLinks(Dialog):
 
 if __name__ == '__main__':
     import sys
+
     from calibre.gui2 import Application
     from calibre.gui2.tweak_book.boss import get_container
     app = Application([])
diff --git a/src/calibre/gui2/tweak_book/download.py b/src/calibre/gui2/tweak_book/download.py
index 46de1d060f..246c5b46c1 100644
--- a/src/calibre/gui2/tweak_book/download.py
+++ b/src/calibre/gui2/tweak_book/download.py
@@ -2,17 +2,20 @@
 # License: GPLv3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>
 
 
+from qt.core import (
+    QDialogButtonBox, QGridLayout, QIcon, QLabel, QListWidget, QListWidgetItem,
+    QProgressBar, QScrollArea, QSize, Qt, QVBoxLayout, QWidget, pyqtSignal,
+)
 from threading import Thread
 
-from qt.core import (
-    pyqtSignal, QWidget, QListWidget, QListWidgetItem, QLabel, Qt,
-    QVBoxLayout, QScrollArea, QProgressBar, QGridLayout, QSize, QIcon, QDialogButtonBox)
-
+from calibre.ebooks.oeb.polish.download import (
+    download_external_resources, get_external_resources, replace_resources,
+)
 from calibre.gui2 import error_dialog, info_dialog, warning_dialog
+from calibre.gui2.progress_indicator import WaitStack
 from calibre.gui2.tweak_book import current_container
 from calibre.gui2.tweak_book.widgets import Dialog
-from calibre.gui2.progress_indicator import WaitStack
-from calibre.ebooks.oeb.polish.download import get_external_resources, download_external_resources, replace_resources
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems
 
 
@@ -258,8 +261,9 @@ class DownloadResources(Dialog):
 
 
 if __name__ == '__main__':
-    from calibre.gui2 import Application
     import sys
+
+    from calibre.gui2 import Application
     app = Application([])
     from calibre.gui2.tweak_book import set_current_container
     from calibre.gui2.tweak_book.boss import get_container
diff --git a/src/calibre/gui2/tweak_book/file_list.py b/src/calibre/gui2/tweak_book/file_list.py
index 437058eb76..1eb9dfef9f 100644
--- a/src/calibre/gui2/tweak_book/file_list.py
+++ b/src/calibre/gui2/tweak_book/file_list.py
@@ -13,31 +13,31 @@ from qt.core import (
     QFormLayout, QGridLayout, QIcon, QInputDialog, QItemSelectionModel, QLabel,
     QLineEdit, QListWidget, QListWidgetItem, QMenu, QPainter, QPixmap, QRadioButton,
     QScrollArea, QSize, QSpinBox, QStyle, QStyledItemDelegate, Qt, QTimer, QTreeView,
-    QTreeWidget, QTreeWidgetItem, QVBoxLayout, QWidget, pyqtSignal, sip
+    QTreeWidget, QTreeWidgetItem, QVBoxLayout, QWidget, pyqtSignal, sip,
 )
 
 from calibre import human_readable, sanitize_file_name
 from calibre.ebooks.oeb.base import OEB_DOCS, OEB_STYLES
 from calibre.ebooks.oeb.polish.cover import (
-    get_cover_page_name, get_raster_cover_name, is_raster_image
+    get_cover_page_name, get_raster_cover_name, is_raster_image,
 )
 from calibre.ebooks.oeb.polish.css import add_stylesheet_links
 from calibre.ebooks.oeb.polish.replace import (
-    get_recommended_folders, get_spine_order_for_all_files
+    get_recommended_folders, get_spine_order_for_all_files,
 )
 from calibre.ebooks.oeb.polish.utils import OEB_FONTS, guess_type
 from calibre.gui2 import (
     choose_dir, choose_files, choose_save_file, elided_text, error_dialog,
-    make_view_use_window_background, question_dialog
+    make_view_use_window_background, question_dialog,
 )
 from calibre.gui2.tweak_book import (
-    CONTAINER_DND_MIMETYPE, current_container, editors, tprefs
+    CONTAINER_DND_MIMETYPE, current_container, editors, tprefs,
 )
 from calibre.gui2.tweak_book.editor import syntax_from_mime
 from calibre.gui2.tweak_book.templates import template_for
 from calibre.utils.fonts.utils import get_font_names
-from calibre.utils.localization import pgettext
 from calibre.utils.icu import numeric_sort_key
+from calibre.utils.localization import ngettext, pgettext
 from calibre_extensions.progress_indicator import set_no_activate_on_click
 from polyglot.binary import as_hex_unicode
 from polyglot.builtins import iteritems
diff --git a/src/calibre/gui2/tweak_book/manage_fonts.py b/src/calibre/gui2/tweak_book/manage_fonts.py
index 14cfaaa032..8e28d8b8e6 100644
--- a/src/calibre/gui2/tweak_book/manage_fonts.py
+++ b/src/calibre/gui2/tweak_book/manage_fonts.py
@@ -22,6 +22,7 @@ from calibre.gui2.widgets import BusyCursor
 from calibre.utils.fonts.metadata import FontMetadata, UnsupportedFont
 from calibre.utils.fonts.scanner import NoFonts, font_scanner
 from calibre.utils.icu import lower as icu_lower, primary_sort_key as sort_key
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems
 
 
diff --git a/src/calibre/gui2/tweak_book/preferences.py b/src/calibre/gui2/tweak_book/preferences.py
index 5b4bcf5a0c..506d316538 100644
--- a/src/calibre/gui2/tweak_book/preferences.py
+++ b/src/calibre/gui2/tweak_book/preferences.py
@@ -5,30 +5,34 @@ __license__ = 'GPL v3'
 __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
 import numbers
-from operator import attrgetter, methodcaller
-from functools import partial
 from collections import namedtuple
-from polyglot.builtins import iteritems, itervalues
-from itertools import product
 from copy import copy, deepcopy
-
+from functools import partial
+from itertools import product
+from operator import attrgetter, methodcaller
 from qt.core import (
-    QDialog, QGridLayout, QStackedWidget, QDialogButtonBox, QListWidget,
-    QListWidgetItem, QIcon, QWidget, QSize, QFormLayout, Qt, QSpinBox, QListView,
-    QCheckBox, pyqtSignal, QDoubleSpinBox, QComboBox, QLabel, QFont,
-    QFontComboBox, QPushButton, QSizePolicy, QHBoxLayout, QGroupBox, QAbstractItemView,
-    QToolButton, QVBoxLayout, QSpacerItem, QTimer, QRadioButton)
+    QAbstractItemView, QCheckBox, QComboBox, QDialog, QDialogButtonBox, QDoubleSpinBox,
+    QFont, QFontComboBox, QFormLayout, QGridLayout, QGroupBox, QHBoxLayout, QIcon,
+    QLabel, QListView, QListWidget, QListWidgetItem, QPushButton, QRadioButton, QSize,
+    QSizePolicy, QSpacerItem, QSpinBox, QStackedWidget, Qt, QTimer, QToolButton,
+    QVBoxLayout, QWidget, pyqtSignal,
+)
 
 from calibre import prepare_string_for_xml
-from calibre.utils.localization import get_lang
 from calibre.gui2 import info_dialog
-from calibre.gui2.keyboard import ShortcutConfig
-from calibre.gui2.tweak_book import tprefs, toolbar_actions, editor_toolbar_actions, actions
-from calibre.gui2.tweak_book.editor.themes import default_theme, all_theme_names, ThemeEditor
-from calibre.gui2.tweak_book.spell import ManageDictionaries
 from calibre.gui2.font_family_chooser import FontFamilyChooser
+from calibre.gui2.keyboard import ShortcutConfig
+from calibre.gui2.tweak_book import (
+    actions, editor_toolbar_actions, toolbar_actions, tprefs,
+)
+from calibre.gui2.tweak_book.editor.themes import (
+    ThemeEditor, all_theme_names, default_theme,
+)
+from calibre.gui2.tweak_book.spell import ManageDictionaries
 from calibre.gui2.tweak_book.widgets import Dialog
 from calibre.gui2.widgets2 import ColorButton
+from calibre.utils.localization import get_lang, ngettext
+from polyglot.builtins import iteritems, itervalues
 
 
 class BasicSettings(QWidget):  # {{{
@@ -348,7 +352,7 @@ class PreviewSettings(BasicSettings):  # {{{
 
         def default_font(which):
             if not self.default_font_settings:
-                from qt.webengine import QWebEngineSettings, QWebEnginePage
+                from qt.webengine import QWebEnginePage, QWebEngineSettings
                 page = QWebEnginePage()
                 s = page.settings()
                 self.default_font_settings = {
@@ -672,8 +676,9 @@ class TemplatesDialog(Dialog):  # {{{
         Dialog.__init__(self, _('Customize templates'), 'customize-templates', parent=parent)
 
     def setup_ui(self):
-        from calibre.gui2.tweak_book.templates import DEFAULT_TEMPLATES
         from calibre.gui2.tweak_book.editor.text import TextEdit
+        from calibre.gui2.tweak_book.templates import DEFAULT_TEMPLATES
+
         # Cannot use QFormLayout as it does not play nice with TextEdit on windows
         self.l = l = QVBoxLayout(self)
 
diff --git a/src/calibre/gui2/update.py b/src/calibre/gui2/update.py
index 25770d7c17..237f363734 100644
--- a/src/calibre/gui2/update.py
+++ b/src/calibre/gui2/update.py
@@ -4,20 +4,20 @@ __copyright__ = '2008, Kovid Goyal <kovid at kovidgoyal.net>'
 import re
 import ssl
 from qt.core import (
-    QCheckBox, QDialog, QDialogButtonBox, QGridLayout, QIcon, QLabel, QObject, Qt,
-    QUrl, pyqtSignal
+    QCheckBox, QDialog, QDialogButtonBox, QGridLayout, QIcon, QLabel, QObject, Qt, QUrl,
+    pyqtSignal,
 )
 from threading import Event, Thread
 
 from calibre import as_unicode, prints
 from calibre.constants import (
-    __appname__, __version__, ismacos, isportable, iswindows, numeric_version
+    __appname__, __version__, ismacos, isportable, iswindows, numeric_version,
 )
 from calibre.gui2 import config, dynamic, icon_resource_manager, open_url
 from calibre.gui2.dialogs.plugin_updater import get_plugin_updates_available
 from calibre.utils.config import prefs
 from calibre.utils.https import get_https_resource_securely
-from calibre.utils.localization import localize_website_link
+from calibre.utils.localization import localize_website_link, ngettext
 from calibre.utils.serialize import msgpack_dumps, msgpack_loads
 from polyglot.binary import as_hex_unicode, from_hex_bytes
 
@@ -168,7 +168,7 @@ class UpdateNotification(QDialog):
 
     def get_plugins(self):
         from calibre.gui2.dialogs.plugin_updater import (
-            FILTER_UPDATE_AVAILABLE, PluginUpdaterDialog
+            FILTER_UPDATE_AVAILABLE, PluginUpdaterDialog,
         )
         d = PluginUpdaterDialog(self.parent(),
                 initial_filter=FILTER_UPDATE_AVAILABLE)
@@ -238,7 +238,7 @@ class UpdateMixin:
         elif has_plugin_updates:
             if force:
                 from calibre.gui2.dialogs.plugin_updater import (
-                    FILTER_UPDATE_AVAILABLE, PluginUpdaterDialog
+                    FILTER_UPDATE_AVAILABLE, PluginUpdaterDialog,
                 )
                 d = PluginUpdaterDialog(self,
                         initial_filter=FILTER_UPDATE_AVAILABLE)
diff --git a/src/calibre/gui2/viewer/highlights.py b/src/calibre/gui2/viewer/highlights.py
index 3776885efa..e652764857 100644
--- a/src/calibre/gui2/viewer/highlights.py
+++ b/src/calibre/gui2/viewer/highlights.py
@@ -8,26 +8,27 @@ from functools import lru_cache
 from itertools import chain
 from qt.core import (
     QAbstractItemView, QColor, QDialog, QFont, QHBoxLayout, QIcon, QImage,
-    QItemSelectionModel, QKeySequence, QLabel, QMenu, QPainter, QPainterPath,
-    QPalette, QPixmap, QPushButton, QRect, QSizePolicy, QStyle, Qt, QTextCursor,
-    QTextEdit, QTreeWidget, QTreeWidgetItem, QVBoxLayout, QWidget, pyqtSignal
+    QItemSelectionModel, QKeySequence, QLabel, QMenu, QPainter, QPainterPath, QPalette,
+    QPixmap, QPushButton, QRect, QSizePolicy, QStyle, Qt, QTextCursor, QTextEdit,
+    QTreeWidget, QTreeWidgetItem, QVBoxLayout, QWidget, pyqtSignal,
 )
 
 from calibre.constants import (
-    builtin_colors_dark, builtin_colors_light, builtin_decorations
+    builtin_colors_dark, builtin_colors_light, builtin_decorations,
 )
 from calibre.ebooks.epub.cfi.parse import cfi_sort_key
 from calibre.gui2 import error_dialog, is_dark_theme, safe_open_url
 from calibre.gui2.dialogs.confirm_delete import confirm
 from calibre.gui2.gestures import GestureManager
 from calibre.gui2.library.annotations import (
-    Details, Export as ExportBase, render_highlight_as_text, render_notes
+    Details, Export as ExportBase, render_highlight_as_text, render_notes,
 )
 from calibre.gui2.viewer import link_prefix_for_location_links
 from calibre.gui2.viewer.config import vprefs
 from calibre.gui2.viewer.search import SearchInput
 from calibre.gui2.viewer.shortcuts import get_shortcut_for, index_to_key_sequence
 from calibre.gui2.widgets2 import Dialog
+from calibre.utils.localization import ngettext
 from calibre_extensions.progress_indicator import set_no_activate_on_click
 
 decoration_cache = {}
diff --git a/src/calibre/gui2/viewer/search.py b/src/calibre/gui2/viewer/search.py
index 112d381118..b59118b3ea 100644
--- a/src/calibre/gui2/viewer/search.py
+++ b/src/calibre/gui2/viewer/search.py
@@ -7,7 +7,7 @@ from collections import Counter, OrderedDict
 from html import escape
 from qt.core import (
     QAbstractItemView, QCheckBox, QComboBox, QFont, QHBoxLayout, QIcon, QLabel, Qt,
-    QToolButton, QTreeWidget, QTreeWidgetItem, QVBoxLayout, QWidget, pyqtSignal
+    QToolButton, QTreeWidget, QTreeWidgetItem, QVBoxLayout, QWidget, pyqtSignal,
 )
 from threading import Thread
 
@@ -19,6 +19,7 @@ from calibre.gui2.viewer.config import vprefs
 from calibre.gui2.viewer.web_view import get_data, get_manifest
 from calibre.gui2.viewer.widgets import ResultsDelegate, SearchBox
 from calibre.utils.icu import primary_collator_without_punctuation
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems
 from polyglot.functools import lru_cache
 from polyglot.queue import Queue
@@ -363,6 +364,7 @@ def search_in_name(name, search_query, ctx_size=75):
 
     else:
         spans = []
+
         def miter():
             return spans
         if raw:
diff --git a/src/calibre/library/catalogs/epub_mobi_builder.py b/src/calibre/library/catalogs/epub_mobi_builder.py
index 79a6964821..cf6578c5b5 100644
--- a/src/calibre/library/catalogs/epub_mobi_builder.py
+++ b/src/calibre/library/catalogs/epub_mobi_builder.py
@@ -35,8 +35,10 @@ from calibre.utils.date import (
 )
 from calibre.utils.filenames import ascii_text, shorten_components_to
 from calibre.utils.formatter import TemplateFormatter
-from calibre.utils.icu import capitalize, collation_order, sort_key, upper as icu_upper
-from calibre.utils.localization import get_lang, lang_as_iso639_1
+from calibre.utils.icu import (
+    capitalize, collation_order, sort_key, title_case as icu_title, upper as icu_upper,
+)
+from calibre.utils.localization import get_lang, lang_as_iso639_1, ngettext
 from calibre.utils.resources import get_image_path as I, get_path as P
 from calibre.utils.xml_parse import safe_xml_fromstring
 from calibre.utils.zipfile import ZipFile
diff --git a/src/calibre/library/field_metadata.py b/src/calibre/library/field_metadata.py
index f1efea9a9f..07f27a0935 100644
--- a/src/calibre/library/field_metadata.py
+++ b/src/calibre/library/field_metadata.py
@@ -9,6 +9,7 @@ from collections import OrderedDict
 
 from calibre.utils.config_base import tweaks
 from calibre.utils.icu import lower as icu_lower
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems, itervalues
 
 category_icon_map = {
diff --git a/src/calibre/srv/manage_users_cli.py b/src/calibre/srv/manage_users_cli.py
index f3082752b0..7544c9901d 100644
--- a/src/calibre/srv/manage_users_cli.py
+++ b/src/calibre/srv/manage_users_cli.py
@@ -5,8 +5,9 @@ import sys
 from functools import partial
 
 from calibre import prints
-from calibre.constants import preferred_encoding, iswindows
+from calibre.constants import iswindows, preferred_encoding
 from calibre.utils.config import OptionParser
+from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems
 
 
diff --git a/src/calibre/srv/opds.py b/src/calibre/srv/opds.py
index 8e19a7b561..2ec3e0d242 100644
--- a/src/calibre/srv/opds.py
+++ b/src/calibre/srv/opds.py
@@ -24,6 +24,7 @@ from calibre.srv.utils import Offsets, get_library_data, http_date
 from calibre.utils.config import prefs
 from calibre.utils.date import as_utc, is_date_undefined, timestampfromdt
 from calibre.utils.icu import sort_key
+from calibre.utils.localization import ngettext
 from calibre.utils.search_query_parser import ParseException
 from calibre.utils.xml_parse import safe_xml_fromstring
 from polyglot.binary import as_hex_unicode, from_hex_unicode