From 779e69a38cf4bbe1c32037dc9e84628f761bab42 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Mon, 9 Jan 2023 21:38:45 +0530
Subject: [PATCH] Remove use of global icu_upper/lower

---
 src/calibre/db/adding.py                      |  3 ++
 src/calibre/db/backend.py                     |  2 +-
 src/calibre/db/cache.py                       |  6 +--
 src/calibre/db/categories.py                  |  8 ++--
 src/calibre/db/legacy.py                      | 19 ++++++---
 src/calibre/db/search.py                      | 20 ++++++----
 src/calibre/db/tables.py                      |  7 ++--
 src/calibre/db/utils.py                       | 15 ++++---
 src/calibre/db/write.py                       |  9 +++--
 src/calibre/devices/mtp/books.py              |  2 +-
 src/calibre/devices/mtp/driver.py             | 21 ++++++----
 src/calibre/ebooks/metadata/author_mapper.py  |  4 +-
 src/calibre/ebooks/metadata/book/base.py      | 16 +++++---
 src/calibre/ebooks/metadata/opf2.py           | 40 ++++++++++++-------
 src/calibre/ebooks/metadata/sources/amazon.py | 26 +++++++-----
 src/calibre/ebooks/metadata/tag_mapper.py     |  2 +
 src/calibre/ebooks/metadata/worker.py         |  1 +
 src/calibre/ebooks/oeb/polish/css.py          | 14 +++----
 src/calibre/ebooks/oeb/polish/embed.py        |  4 +-
 src/calibre/ebooks/oeb/polish/stats.py        |  9 +++--
 .../ebooks/oeb/polish/tests/cascade.py        | 14 ++++---
 src/calibre/ebooks/oeb/polish/utils.py        |  2 +
 .../ebooks/oeb/transforms/manglecase.py       |  6 +--
 src/calibre/gui2/actions/similar_books.py     |  1 +
 src/calibre/gui2/add.py                       |  1 +
 src/calibre/gui2/author_mapper.py             |  2 +-
 src/calibre/gui2/custom_column_widgets.py     | 28 +++++++------
 .../gui2/device_drivers/mtp_folder_browser.py |  8 ++--
 src/calibre/gui2/dialogs/authors_edit.py      | 11 ++---
 .../gui2/dialogs/edit_authors_dialog.py       | 15 ++++---
 src/calibre/gui2/dialogs/metadata_bulk.py     | 14 ++++---
 src/calibre/gui2/dialogs/plugin_updater.py    | 11 ++---
 .../gui2/dialogs/saved_search_editor.py       |  6 +--
 src/calibre/gui2/dialogs/tag_categories.py    |  7 ++--
 src/calibre/gui2/dialogs/tag_list_editor.py   | 18 +++++----
 src/calibre/gui2/dialogs/template_dialog.py   |  2 +-
 src/calibre/gui2/font_family_chooser.py       |  9 +++--
 src/calibre/gui2/metadata/diff.py             |  4 +-
 src/calibre/gui2/preferences/search.py        | 11 ++---
 src/calibre/gui2/store/search/models.py       | 15 +++----
 src/calibre/gui2/tag_browser/model.py         | 11 ++---
 src/calibre/gui2/tag_mapper.py                |  6 +--
 src/calibre/gui2/toc/main.py                  | 17 ++++----
 src/calibre/gui2/tweak_book/manage_fonts.py   | 17 ++++----
 src/calibre/library/caches.py                 | 28 +++++++------
 .../library/catalogs/epub_mobi_builder.py     |  2 +-
 src/calibre/library/database2.py              |  2 +-
 src/calibre/library/field_metadata.py         |  1 +
 src/calibre/srv/metadata.py                   | 14 +++----
 src/calibre/utils/fonts/scanner.py            |  2 +-
 src/calibre/utils/formatter_functions.py      |  2 +-
 src/calibre/utils/icu.py                      |  2 +-
 src/calibre/utils/matcher.py                  | 20 ++++++----
 53 files changed, 317 insertions(+), 220 deletions(-)

diff --git a/src/calibre/db/adding.py b/src/calibre/db/adding.py
index 58452b32a0..b78e6fdadb 100644
--- a/src/calibre/db/adding.py
+++ b/src/calibre/db/adding.py
@@ -15,6 +15,7 @@ from calibre import prints
 from calibre.constants import filesystem_encoding, ismacos, iswindows
 from calibre.ebooks import BOOK_EXTENSIONS
 from calibre.utils.filenames import make_long_path_useable
+from calibre.utils.icu import lower as icu_lower
 from polyglot.builtins import itervalues
 
 
@@ -48,10 +49,12 @@ def compile_rule(rule):
                 return icu_lower(filename).endswith(q)
     elif 'glob' in mt:
         q = compile_glob(rule['query'])
+
         def func(filename):
             return (q.match(filename) is not None)
     else:
         q = re.compile(rule['query'])
+
         def func(filename):
             return (q.match(filename) is not None)
     ans = func
diff --git a/src/calibre/db/backend.py b/src/calibre/db/backend.py
index f8d2b7ab09..614abdbcdc 100644
--- a/src/calibre/db/backend.py
+++ b/src/calibre/db/backend.py
@@ -46,7 +46,7 @@ from calibre.utils.formatter_functions import (
     compile_user_template_functions, formatter_functions, load_user_template_functions,
     unload_user_template_functions,
 )
-from calibre.utils.icu import sort_key
+from calibre.utils.icu import lower as icu_lower, sort_key
 from calibre.utils.resources import get_path as P
 from polyglot.builtins import (
     cmp, iteritems, itervalues, native_string_type, reraise, string_or_bytes,
diff --git a/src/calibre/db/cache.py b/src/calibre/db/cache.py
index c7508026bc..cab398e9fa 100644
--- a/src/calibre/db/cache.py
+++ b/src/calibre/db/cache.py
@@ -24,7 +24,7 @@ from time import monotonic, sleep, time
 from calibre import as_unicode, detect_ncpus, isbytestring
 from calibre.constants import iswindows, preferred_encoding
 from calibre.customize.ui import (
-    run_plugins_on_import, run_plugins_on_postadd, run_plugins_on_postimport
+    run_plugins_on_import, run_plugins_on_postadd, run_plugins_on_postimport,
 )
 from calibre.db import SPOOL_SIZE, _get_next_series_num_for_list
 from calibre.db.annotations import merge_annotations
@@ -34,7 +34,7 @@ from calibre.db.fields import IDENTITY, InvalidLinkTable, create_field
 from calibre.db.lazy import FormatMetadata, FormatsList, ProxyMetadata
 from calibre.db.listeners import EventDispatcher, EventType
 from calibre.db.locking import (
-    DowngradeLockError, LockingError, SafeReadLock, create_locks, try_lock
+    DowngradeLockError, LockingError, SafeReadLock, create_locks, try_lock,
 )
 from calibre.db.search import Search
 from calibre.db.tables import VirtualTable
@@ -47,7 +47,7 @@ from calibre.ebooks.metadata.opf2 import metadata_to_opf
 from calibre.ptempfile import PersistentTemporaryFile, SpooledTemporaryFile, base_dir
 from calibre.utils.config import prefs, tweaks
 from calibre.utils.date import UNDEFINED_DATE, now as nowf, utcnow
-from calibre.utils.icu import sort_key
+from calibre.utils.icu import lower as icu_lower, sort_key
 from calibre.utils.localization import canonicalize_lang
 from polyglot.builtins import cmp, iteritems, itervalues, string_or_bytes
 
diff --git a/src/calibre/db/categories.py b/src/calibre/db/categories.py
index 07b7c50cd5..f0c8636348 100644
--- a/src/calibre/db/categories.py
+++ b/src/calibre/db/categories.py
@@ -8,11 +8,13 @@ __docformat__ = 'restructuredtext en'
 import copy
 from collections import OrderedDict
 from functools import partial
-from polyglot.builtins import iteritems, native_string_type
 
 from calibre.ebooks.metadata import author_to_author_sort
-from calibre.utils.config_base import tweaks, prefs
-from calibre.utils.icu import sort_key, collation_order
+from calibre.utils.config_base import prefs, tweaks
+from calibre.utils.icu import (
+    collation_order, lower as icu_lower, sort_key, upper as icu_upper,
+)
+from polyglot.builtins import iteritems, native_string_type
 
 CATEGORY_SORTS = ('name', 'popularity', 'rating')  # This has to be a tuple not a set
 
diff --git a/src/calibre/db/legacy.py b/src/calibre/db/legacy.py
index 7567050030..a333bb3d6c 100644
--- a/src/calibre/db/legacy.py
+++ b/src/calibre/db/legacy.py
@@ -4,24 +4,30 @@
 __license__ = 'GPL v3'
 __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
-import os, traceback, weakref
-from polyglot.builtins import iteritems
+import os
+import traceback
+import weakref
 from collections.abc import MutableMapping
 
 from calibre import force_unicode, isbytestring
 from calibre.constants import preferred_encoding
-from calibre.db import _get_next_series_num_for_list, _get_series_values, get_data_as_dict
+from calibre.db import (
+    _get_next_series_num_for_list, _get_series_values, get_data_as_dict,
+)
 from calibre.db.adding import (
-    find_books_in_directory, import_book_directory_multiple,
-    import_book_directory, recursive_import, add_catalog, add_news)
+    add_catalog, add_news, find_books_in_directory, import_book_directory,
+    import_book_directory_multiple, recursive_import,
+)
 from calibre.db.backend import DB, set_global_state as backend_set_global_state
 from calibre.db.cache import Cache
-from calibre.db.errors import NoSuchFormat
 from calibre.db.categories import CATEGORY_SORTS
+from calibre.db.errors import NoSuchFormat
 from calibre.db.view import View
 from calibre.db.write import clean_identifier, get_series_values
 from calibre.utils.date import utcnow
+from calibre.utils.icu import lower as icu_lower
 from calibre.utils.search_query_parser import set_saved_searches
+from polyglot.builtins import iteritems
 
 
 def cleanup_tags(tags):
@@ -156,6 +162,7 @@ class ThreadSafePrefs(MutableMapping):
         if isinstance(raw, bytes):
             raw = raw.decode(preferred_encoding)
         import json
+
         from calibre.utils.config import from_json
         return json.loads(raw, object_hook=from_json)
 
diff --git a/src/calibre/db/search.py b/src/calibre/db/search.py
index 60d48cee3f..b4de2f014b 100644
--- a/src/calibre/db/search.py
+++ b/src/calibre/db/search.py
@@ -5,18 +5,22 @@ __license__   = 'GPL v3'
 __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-import regex, weakref, operator
-from functools import partial
+import operator
+import regex
+import weakref
+from collections import OrderedDict, deque
 from datetime import timedelta
-from collections import deque, OrderedDict
+from functools import partial
 
-from calibre.constants import preferred_encoding, DEBUG
+from calibre.constants import DEBUG, preferred_encoding
 from calibre.db.utils import force_to_bool
 from calibre.utils.config_base import prefs
-from calibre.utils.date import parse_date, UNDEFINED_DATE, now, dt_as_local
-from calibre.utils.icu import primary_no_punc_contains, primary_contains, sort_key
-from calibre.utils.localization import lang_map, canonicalize_lang
-from calibre.utils.search_query_parser import SearchQueryParser, ParseException
+from calibre.utils.date import UNDEFINED_DATE, dt_as_local, now, parse_date
+from calibre.utils.icu import (
+    lower as icu_lower, primary_contains, primary_no_punc_contains, sort_key,
+)
+from calibre.utils.localization import canonicalize_lang, lang_map
+from calibre.utils.search_query_parser import ParseException, SearchQueryParser
 from polyglot.builtins import iteritems, string_or_bytes
 
 CONTAINS_MATCH = 0
diff --git a/src/calibre/db/tables.py b/src/calibre/db/tables.py
index cff608b312..4a2a4da706 100644
--- a/src/calibre/db/tables.py
+++ b/src/calibre/db/tables.py
@@ -6,13 +6,14 @@ __copyright__ = '2011, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
 import numbers
-from datetime import datetime, timedelta
 from collections import defaultdict
+from datetime import datetime, timedelta
 
-from calibre.utils.date import parse_date, UNDEFINED_DATE, utc_tz
 from calibre.ebooks.metadata import author_to_author_sort
-from polyglot.builtins import iteritems, itervalues
+from calibre.utils.date import UNDEFINED_DATE, parse_date, utc_tz
+from calibre.utils.icu import lower as icu_lower
 from calibre_extensions.speedup import parse_date as _c_speedup
+from polyglot.builtins import iteritems, itervalues
 
 
 def c_parse(val):
diff --git a/src/calibre/db/utils.py b/src/calibre/db/utils.py
index 2d3fc1deae..8c8a449284 100644
--- a/src/calibre/db/utils.py
+++ b/src/calibre/db/utils.py
@@ -4,16 +4,21 @@
 __license__ = 'GPL v3'
 __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
-import os, errno, sys, re
-from locale import localeconv
+import errno
+import os
+import re
+import sys
 from collections import OrderedDict, namedtuple
-from polyglot.builtins import iteritems, itervalues, string_or_bytes
+from locale import localeconv
 from threading import Lock
 
 from calibre import as_unicode, prints
-from calibre.constants import cache_dir, get_windows_number_formats, iswindows, preferred_encoding
-
+from calibre.constants import (
+    cache_dir, get_windows_number_formats, iswindows, preferred_encoding,
+)
+from calibre.utils.icu import lower as icu_lower
 from calibre.utils.localization import canonicalize_lang
+from polyglot.builtins import iteritems, itervalues, string_or_bytes
 
 
 def force_to_bool(val):
diff --git a/src/calibre/db/write.py b/src/calibre/db/write.py
index 5f97dd80ce..8b240316ff 100644
--- a/src/calibre/db/write.py
+++ b/src/calibre/db/write.py
@@ -6,16 +6,17 @@ __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
 import re
-from functools import partial
 from datetime import datetime
-from polyglot.builtins import iteritems, itervalues
+from functools import partial
 
 from calibre.constants import preferred_encoding
 from calibre.ebooks.metadata import author_to_author_sort, title_sort
 from calibre.utils.date import (
-    parse_only_date, parse_date, UNDEFINED_DATE, isoformat, is_date_undefined)
+    UNDEFINED_DATE, is_date_undefined, isoformat, parse_date, parse_only_date,
+)
+from calibre.utils.icu import lower as icu_lower, strcmp
 from calibre.utils.localization import canonicalize_lang
-from calibre.utils.icu import strcmp
+from polyglot.builtins import iteritems, itervalues
 
 missing = object()
 
diff --git a/src/calibre/devices/mtp/books.py b/src/calibre/devices/mtp/books.py
index 3384a830d5..44a6ca0495 100644
--- a/src/calibre/devices/mtp/books.py
+++ b/src/calibre/devices/mtp/books.py
@@ -12,6 +12,7 @@ from calibre.ebooks.metadata import title_sort
 from calibre.ebooks.metadata.book.base import Metadata
 from calibre.ebooks.metadata.book.json_codec import JsonCodec
 from calibre.utils.date import utcnow
+from calibre.utils.icu import lower as icu_lower
 
 
 class BookList(BL):
@@ -73,4 +74,3 @@ class Book(Metadata):
 
 class JSONCodec(JsonCodec):
     pass
-
diff --git a/src/calibre/devices/mtp/driver.py b/src/calibre/devices/mtp/driver.py
index 6d12c601e0..5d0e53d8de 100644
--- a/src/calibre/devices/mtp/driver.py
+++ b/src/calibre/devices/mtp/driver.py
@@ -5,7 +5,11 @@ __license__   = 'GPL v3'
 __copyright__ = '2012, Kovid Goyal <kovid at kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-import json, traceback, posixpath, importlib, os
+import importlib
+import json
+import os
+import posixpath
+import traceback
 from io import BytesIO
 
 from calibre import prints
@@ -13,9 +17,10 @@ from calibre.constants import iswindows, numeric_version
 from calibre.devices.errors import PathError
 from calibre.devices.mtp.base import debug
 from calibre.devices.mtp.defaults import DeviceDefaults
-from calibre.ptempfile import SpooledTemporaryFile, PersistentTemporaryDirectory
+from calibre.ptempfile import PersistentTemporaryDirectory, SpooledTemporaryFile
 from calibre.utils.filenames import shorten_components_to
-from polyglot.builtins import iteritems, itervalues, as_bytes
+from calibre.utils.icu import lower as icu_lower
+from polyglot.builtins import as_bytes, iteritems, itervalues
 
 BASE = importlib.import_module('calibre.devices.mtp.%s.driver'%(
     'windows' if iswindows else 'unix')).MTP_DEVICE
@@ -153,9 +158,10 @@ class MTP_DEVICE(BASE):
 
     # Device information {{{
     def _update_drive_info(self, storage, location_code, name=None):
-        from calibre.utils.date import isoformat, now
-        from calibre.utils.config import from_json, to_json
         import uuid
+
+        from calibre.utils.config import from_json, to_json
+        from calibre.utils.date import isoformat, now
         f = storage.find_path(self.calibre_file_paths['driveinfo'].split('/'))
         dinfo = {}
         if f is not None:
@@ -213,8 +219,7 @@ class MTP_DEVICE(BASE):
         self.report_progress(0, msg)
 
     def books(self, oncard=None, end_session=True):
-        from calibre.devices.mtp.books import JSONCodec
-        from calibre.devices.mtp.books import BookList, Book
+        from calibre.devices.mtp.books import Book, BookList, JSONCodec
         self.report_progress(0, _('Listing files, this can take a while'))
         self.get_driveinfo()  # Ensure driveinfo is loaded
         sid = {'carda':self._carda_id, 'cardb':self._cardb_id}.get(oncard,
@@ -288,8 +293,8 @@ class MTP_DEVICE(BASE):
         return bl
 
     def read_file_metadata(self, mtp_file):
-        from calibre.ebooks.metadata.meta import get_metadata
         from calibre.customize.ui import quick_metadata
+        from calibre.ebooks.metadata.meta import get_metadata
         ext = mtp_file.name.rpartition('.')[-1].lower()
         stream = self.get_mtp_file(mtp_file)
         with quick_metadata:
diff --git a/src/calibre/ebooks/metadata/author_mapper.py b/src/calibre/ebooks/metadata/author_mapper.py
index e7705b539a..9286f160f7 100644
--- a/src/calibre/ebooks/metadata/author_mapper.py
+++ b/src/calibre/ebooks/metadata/author_mapper.py
@@ -5,7 +5,9 @@
 import re
 from collections import deque
 
-from calibre.utils.icu import capitalize, lower, upper
+from calibre.utils.icu import (
+    capitalize, lower, lower as icu_lower, upper, upper as icu_upper,
+)
 
 
 def cap_author_token(token):
diff --git a/src/calibre/ebooks/metadata/book/base.py b/src/calibre/ebooks/metadata/book/base.py
index bc17b256f0..ed6b15e1e0 100644
--- a/src/calibre/ebooks/metadata/book/base.py
+++ b/src/calibre/ebooks/metadata/book/base.py
@@ -5,15 +5,17 @@ __license__   = 'GPL v3'
 __copyright__ = '2010, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-import copy, traceback
+import copy
+import traceback
 
 from calibre import prints
 from calibre.constants import DEBUG
-from calibre.ebooks.metadata.book import (SC_COPYABLE_FIELDS,
-        SC_FIELDS_COPY_NOT_NULL, STANDARD_METADATA_FIELDS,
-        TOP_LEVEL_IDENTIFIERS, ALL_METADATA_FIELDS)
+from calibre.ebooks.metadata.book import (
+    ALL_METADATA_FIELDS, SC_COPYABLE_FIELDS, SC_FIELDS_COPY_NOT_NULL,
+    STANDARD_METADATA_FIELDS, TOP_LEVEL_IDENTIFIERS,
+)
 from calibre.library.field_metadata import FieldMetadata
-from calibre.utils.icu import sort_key
+from calibre.utils.icu import lower as icu_lower, sort_key
 from polyglot.builtins import iteritems, string_or_bytes
 
 # Special sets used to optimize the performance of getting and setting
@@ -56,6 +58,8 @@ def reset_field_metadata():
 
 def ck(typ):
     return icu_lower(typ).strip().replace(':', '').replace(',', '')
+
+
 def cv(val):
     return val.strip().replace(',', '|')
 
@@ -734,8 +738,8 @@ class Metadata:
         A string representation of this object, suitable for printing to
         console
         '''
-        from calibre.utils.date import isoformat
         from calibre.ebooks.metadata import authors_to_string
+        from calibre.utils.date import isoformat
         ans = []
 
         def fmt(x, y):
diff --git a/src/calibre/ebooks/metadata/opf2.py b/src/calibre/ebooks/metadata/opf2.py
index ce3eb80a4c..d3a7a6744a 100644
--- a/src/calibre/ebooks/metadata/opf2.py
+++ b/src/calibre/ebooks/metadata/opf2.py
@@ -8,21 +8,29 @@ __docformat__ = 'restructuredtext en'
 lxml based OPF parser.
 '''
 
-import re, sys, functools, os, uuid, glob, io, json, copy
-
+import copy
+import functools
+import glob
+import io
+import json
+import os
+import re
+import sys
+import uuid
 from lxml import etree
 
-from calibre.ebooks import escape_xpath_attr
+from calibre import guess_type, prints
 from calibre.constants import __appname__, __version__, filesystem_encoding
+from calibre.ebooks import escape_xpath_attr
+from calibre.ebooks.metadata import MetaInformation, check_isbn, string_to_authors
+from calibre.ebooks.metadata.book.base import Metadata
 from calibre.ebooks.metadata.toc import TOC
 from calibre.ebooks.metadata.utils import parse_opf, pretty_print_opf as _pretty_print
-from calibre.ebooks.metadata import string_to_authors, MetaInformation, check_isbn
-from calibre.ebooks.metadata.book.base import Metadata
-from calibre.utils.date import parse_date, isoformat
-from calibre.utils.localization import get_lang, canonicalize_lang
-from calibre import prints, guess_type
 from calibre.utils.cleantext import clean_ascii_chars, clean_xml_chars
 from calibre.utils.config import tweaks
+from calibre.utils.date import isoformat, parse_date
+from calibre.utils.icu import lower as icu_lower, upper as icu_upper
+from calibre.utils.localization import canonicalize_lang, get_lang
 from calibre.utils.xml_parse import safe_xml_fromstring
 from polyglot.builtins import iteritems
 from polyglot.urllib import unquote, urlparse
@@ -480,9 +488,10 @@ class TitleSortField(MetadataField):
 
 
 def serialize_user_metadata(metadata_elem, all_user_metadata, tail='\n'+(' '*8)):
+    from calibre.ebooks.metadata.book.json_codec import (
+        encode_is_multiple, object_to_unicode,
+    )
     from calibre.utils.config import to_json
-    from calibre.ebooks.metadata.book.json_codec import (object_to_unicode,
-                                                         encode_is_multiple)
 
     for name, fm in all_user_metadata.items():
         try:
@@ -626,8 +635,8 @@ class OPF:  # {{{
     def read_user_metadata(self):
         self._user_metadata_ = {}
         temp = Metadata('x', ['x'])
-        from calibre.utils.config import from_json
         from calibre.ebooks.metadata.book.json_codec import decode_is_multiple
+        from calibre.utils.config import from_json
         elems = self.root.xpath('//*[name() = "meta" and starts-with(@name,'
                 '"calibre:user_metadata:") and @content]')
         for elem in elems:
@@ -1448,7 +1457,8 @@ class OPFCreator(Metadata):
 
         # Actual rendering
         from lxml.builder import ElementMaker
-        from calibre.ebooks.oeb.base import OPF2_NS, DC11_NS, CALIBRE_NS
+
+        from calibre.ebooks.oeb.base import CALIBRE_NS, DC11_NS, OPF2_NS
         DNS = OPF2_NS+'___xx___'
         E = ElementMaker(namespace=DNS, nsmap={None:DNS})
         M = ElementMaker(namespace=DNS,
@@ -1571,9 +1581,10 @@ class OPFCreator(Metadata):
 
 
 def metadata_to_opf(mi, as_string=True, default_lang=None):
-    from lxml import etree
     import textwrap
-    from calibre.ebooks.oeb.base import OPF, DC
+    from lxml import etree
+
+    from calibre.ebooks.oeb.base import DC, OPF
 
     if not mi.application_id:
         mi.application_id = str(uuid.uuid4())
@@ -1652,6 +1663,7 @@ def metadata_to_opf(mi, as_string=True, default_lang=None):
     if mi.tags:
         for tag in mi.tags:
             factory(DC('subject'), tag)
+
     def meta(n, c):
         return factory('meta', name='calibre:' + n, content=c)
     if getattr(mi, 'author_link_map', None) is not None:
diff --git a/src/calibre/ebooks/metadata/sources/amazon.py b/src/calibre/ebooks/metadata/sources/amazon.py
index 3594495184..78a268d784 100644
--- a/src/calibre/ebooks/metadata/sources/amazon.py
+++ b/src/calibre/ebooks/metadata/sources/amazon.py
@@ -4,15 +4,18 @@
 from __future__ import absolute_import, division, print_function, unicode_literals
 
 import re
-import string
 import socket
+import string
 import time
 from functools import partial
+
 try:
     from queue import Empty, Queue
 except ImportError:
     from Queue import Empty, Queue
+
 from threading import Thread
+
 try:
     from urllib.parse import urlparse
 except ImportError:
@@ -24,9 +27,10 @@ from calibre import as_unicode, browser, random_user_agent, xml_replace_entities
 from calibre.ebooks.metadata import check_isbn
 from calibre.ebooks.metadata.book.base import Metadata
 from calibre.ebooks.metadata.sources.base import Option, Source, fixauthors, fixcase
+from calibre.ebooks.oeb.base import urlquote
+from calibre.utils.icu import lower as icu_lower
 from calibre.utils.localization import canonicalize_lang
 from calibre.utils.random_ua import accept_header_for_ua
-from calibre.ebooks.oeb.base import urlquote
 
 
 def sort_matches_preferring_kindle_editions(matches):
@@ -89,9 +93,10 @@ def parse_html(raw):
 
 
 def parse_details_page(url, log, timeout, browser, domain):
-    from calibre.utils.cleantext import clean_ascii_chars
-    from calibre.ebooks.chardet import xml_to_unicode
     from lxml.html import tostring
+
+    from calibre.ebooks.chardet import xml_to_unicode
+    from calibre.utils.cleantext import clean_ascii_chars
     try:
         from calibre.ebooks.metadata.sources.update import search_engines_module
         get_data_for_cached_url = search_engines_module().get_data_for_cached_url
@@ -726,6 +731,7 @@ class Worker(Thread):  # Get details {{{
                 ns = ns[0]
                 if len(ns) == 0 and ns.text:
                     import html5lib
+
                     # html5lib parsed noscript as CDATA
                     ns = html5lib.parseFragment(
                         '<div>%s</div>' % (ns.text), treebuilder='lxml', namespaceHTMLElements=False)[0]
@@ -1271,9 +1277,9 @@ class Amazon(Source):
     def create_query(self, log, title=None, authors=None, identifiers={},  # {{{
                      domain=None, for_amazon=True):
         try:
-            from urllib.parse import urlencode, unquote_plus
+            from urllib.parse import unquote_plus, urlencode
         except ImportError:
-            from urllib import urlencode, unquote_plus
+            from urllib import unquote_plus, urlencode
         if domain is None:
             domain = self.domain
 
@@ -1442,8 +1448,8 @@ class Amazon(Source):
     # }}}
 
     def search_amazon(self, br, testing, log, abort, title, authors, identifiers, timeout):  # {{{
-        from calibre.utils.cleantext import clean_ascii_chars
         from calibre.ebooks.chardet import xml_to_unicode
+        from calibre.utils.cleantext import clean_ascii_chars
         matches = []
         query, domain = self.create_query(log, title=title, authors=authors,
                                           identifiers=identifiers)
@@ -1703,8 +1709,10 @@ class Amazon(Source):
 def manual_tests(domain, **kw):  # {{{
     # To run these test use:
     # calibre-debug -c "from calibre.ebooks.metadata.sources.amazon import *; manual_tests('com')"
-    from calibre.ebooks.metadata.sources.test import (test_identify_plugin,
-                                                      isbn_test, title_test, authors_test, comments_test, series_test)
+    from calibre.ebooks.metadata.sources.test import (
+        authors_test, comments_test, isbn_test, series_test, test_identify_plugin,
+        title_test,
+    )
     all_tests = {}
     all_tests['com'] = [  # {{{
         (   # Paperback with series
diff --git a/src/calibre/ebooks/metadata/tag_mapper.py b/src/calibre/ebooks/metadata/tag_mapper.py
index 198e20ae2b..4d41f1e616 100644
--- a/src/calibre/ebooks/metadata/tag_mapper.py
+++ b/src/calibre/ebooks/metadata/tag_mapper.py
@@ -4,6 +4,8 @@
 
 from collections import deque
 
+from calibre.utils.icu import lower as icu_lower, upper as icu_upper
+
 
 def compile_pat(pat):
     import regex
diff --git a/src/calibre/ebooks/metadata/worker.py b/src/calibre/ebooks/metadata/worker.py
index 2e3de51942..4c9b939949 100644
--- a/src/calibre/ebooks/metadata/worker.py
+++ b/src/calibre/ebooks/metadata/worker.py
@@ -8,6 +8,7 @@ from calibre.customize.ui import run_plugins_on_import
 from calibre.ebooks.metadata.meta import metadata_from_formats
 from calibre.ebooks.metadata.opf2 import metadata_to_opf
 from calibre.utils.filenames import samefile
+from calibre.utils.icu import lower as icu_lower
 
 
 def serialize_metadata_for(paths, tdir, group_id):
diff --git a/src/calibre/ebooks/oeb/polish/css.py b/src/calibre/ebooks/oeb/polish/css.py
index 386f962b23..8155eaeee5 100644
--- a/src/calibre/ebooks/oeb/polish/css.py
+++ b/src/calibre/ebooks/oeb/polish/css.py
@@ -6,18 +6,18 @@ __copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'
 
 import re
 from collections import defaultdict
+from css_parser.css import CSSRule, CSSStyleDeclaration
 from functools import partial
 from operator import itemgetter
 
-from css_parser.css import CSSRule, CSSStyleDeclaration
-from css_selectors import parse, SelectorSyntaxError
-
 from calibre import force_unicode
-from calibre.ebooks.oeb.base import OEB_STYLES, OEB_DOCS, XHTML, css_text
+from calibre.ebooks.oeb.base import OEB_DOCS, OEB_STYLES, XHTML, css_text
 from calibre.ebooks.oeb.normalize_css import normalize_filter_css, normalizers
-from calibre.ebooks.oeb.polish.pretty import pretty_script_or_style, pretty_xml_tree, serialize
-from calibre.utils.icu import numeric_sort_key
-from css_selectors import Select, SelectorError
+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 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/polish/embed.py b/src/calibre/ebooks/oeb/polish/embed.py
index 443933bf7c..3904bd18d3 100644
--- a/src/calibre/ebooks/oeb/polish/embed.py
+++ b/src/calibre/ebooks/oeb/polish/embed.py
@@ -6,12 +6,12 @@ __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
 import sys
-
 from lxml import etree
 
 from calibre import prints
 from calibre.ebooks.oeb.base import XHTML
 from calibre.utils.filenames import ascii_filename
+from calibre.utils.icu import lower as icu_lower
 from polyglot.builtins import iteritems, itervalues, string_or_bytes
 
 props = {'font-family':None, 'font-weight':'normal', 'font-style':'normal', 'font-stretch':'normal'}
@@ -163,7 +163,7 @@ def embed_font(container, font, all_font_rules, report, warned):
     if not isinstance(ff, string_or_bytes):
         ff = ff[0]
     if rule is None:
-        from calibre.utils.fonts.scanner import font_scanner, NoFonts
+        from calibre.utils.fonts.scanner import NoFonts, font_scanner
         if ff in warned:
             return
         try:
diff --git a/src/calibre/ebooks/oeb/polish/stats.py b/src/calibre/ebooks/oeb/polish/stats.py
index 67feeb3b65..91b302ecb2 100644
--- a/src/calibre/ebooks/oeb/polish/stats.py
+++ b/src/calibre/ebooks/oeb/polish/stats.py
@@ -5,15 +5,16 @@ __license__   = 'GPL v3'
 __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
+import regex
 import sys
 from functools import partial
-
 from lxml.etree import tostring
-import regex
 
 from calibre.ebooks.oeb.base import XHTML, css_text
-from calibre.ebooks.oeb.polish.cascade import iterrules, resolve_styles, iterdeclaration
-from calibre.utils.icu import ord_string, safe_chr
+from calibre.ebooks.oeb.polish.cascade import iterdeclaration, iterrules, resolve_styles
+from calibre.utils.icu import (
+    lower as icu_lower, ord_string, safe_chr, upper as icu_upper,
+)
 from polyglot.builtins import iteritems, itervalues
 from tinycss.fonts3 import parse_font_family
 
diff --git a/src/calibre/ebooks/oeb/polish/tests/cascade.py b/src/calibre/ebooks/oeb/polish/tests/cascade.py
index fd2e07c104..ec47d9911b 100644
--- a/src/calibre/ebooks/oeb/polish/tests/cascade.py
+++ b/src/calibre/ebooks/oeb/polish/tests/cascade.py
@@ -4,18 +4,20 @@
 __license__ = 'GPL v3'
 __copyright__ = '2016, Kovid Goyal <kovid at kovidgoyal.net>'
 
+from css_parser import parseStyle
 from functools import partial
 
-from css_parser import parseStyle
-
 from calibre.constants import iswindows
-from calibre.ebooks.oeb.base import OEB_STYLES, OEB_DOCS
-from calibre.ebooks.oeb.polish.cascade import iterrules, resolve_styles, DEFAULTS
+from calibre.ebooks.oeb.base import OEB_DOCS, OEB_STYLES
+from calibre.ebooks.oeb.polish.cascade import DEFAULTS, iterrules, resolve_styles
+from calibre.ebooks.oeb.polish.container import ContainerBase, href_to_name
 from calibre.ebooks.oeb.polish.css import remove_property_value
 from calibre.ebooks.oeb.polish.embed import find_matching_font
-from calibre.ebooks.oeb.polish.container import ContainerBase, href_to_name
-from calibre.ebooks.oeb.polish.stats import StatsCollector, font_keys, normalize_font_properties, prepare_font_rule
+from calibre.ebooks.oeb.polish.stats import (
+    StatsCollector, font_keys, normalize_font_properties, prepare_font_rule,
+)
 from calibre.ebooks.oeb.polish.tests.base import BaseTest
+from calibre.utils.icu import lower as icu_lower
 from calibre.utils.logging import Log, Stream
 from polyglot.builtins import iteritems
 
diff --git a/src/calibre/ebooks/oeb/polish/utils.py b/src/calibre/ebooks/oeb/polish/utils.py
index 955237ce07..afd5e6b6cf 100644
--- a/src/calibre/ebooks/oeb/polish/utils.py
+++ b/src/calibre/ebooks/oeb/polish/utils.py
@@ -8,6 +8,7 @@ import re, os
 from bisect import bisect
 
 from calibre import guess_type as _guess_type, replace_entities
+from calibre.utils.icu import upper as icu_upper
 
 
 BLOCK_TAG_NAMES = frozenset((
@@ -248,6 +249,7 @@ def apply_func_to_match_groups(match, func=icu_upper, handle_entities=handle_ent
     found_groups = False
     i = 0
     parts, pos = [], match.start()
+
     def f(text):
         return handle_entities(text, func)
     while True:
diff --git a/src/calibre/ebooks/oeb/transforms/manglecase.py b/src/calibre/ebooks/oeb/transforms/manglecase.py
index 4b955663c5..835c1939d3 100644
--- a/src/calibre/ebooks/oeb/transforms/manglecase.py
+++ b/src/calibre/ebooks/oeb/transforms/manglecase.py
@@ -6,10 +6,10 @@ __license__   = 'GPL v3'
 __copyright__ = '2008, Marshall T. Vandegrift <llasram@gmail.com>'
 
 from lxml import etree
-from calibre.ebooks.oeb.base import XHTML, XHTML_NS
-from calibre.ebooks.oeb.base import CSS_MIME
-from calibre.ebooks.oeb.base import namespace
+
+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 polyglot.builtins import string_or_bytes
 
 CASE_MANGLER_CSS = """
diff --git a/src/calibre/gui2/actions/similar_books.py b/src/calibre/gui2/actions/similar_books.py
index cc248ba20e..cac3aa2fe6 100644
--- a/src/calibre/gui2/actions/similar_books.py
+++ b/src/calibre/gui2/actions/similar_books.py
@@ -9,6 +9,7 @@ __docformat__ = 'restructuredtext en'
 from qt.core import QToolButton
 
 from calibre.gui2.actions import InterfaceAction
+from calibre.utils.icu import lower as icu_lower
 from polyglot.builtins import string_or_bytes
 
 
diff --git a/src/calibre/gui2/add.py b/src/calibre/gui2/add.py
index 9f0f1bbe4d..b91351c02b 100644
--- a/src/calibre/gui2/add.py
+++ b/src/calibre/gui2/add.py
@@ -31,6 +31,7 @@ from calibre.ptempfile import PersistentTemporaryDirectory
 from calibre.utils import join_with_timeout
 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 polyglot.builtins import iteritems, string_or_bytes
 from polyglot.queue import Empty
diff --git a/src/calibre/gui2/author_mapper.py b/src/calibre/gui2/author_mapper.py
index 1605793d4b..5d26d08a9c 100644
--- a/src/calibre/gui2/author_mapper.py
+++ b/src/calibre/gui2/author_mapper.py
@@ -10,7 +10,7 @@ from calibre.gui2 import Application, elided_text
 from calibre.gui2.tag_mapper import (
     RuleEdit as RuleEditBase, RuleEditDialog as RuleEditDialogBase,
     RuleItem as RuleItemBase, Rules as RulesBase, RulesDialog as RulesDialogBase,
-    Tester as TesterBase
+    Tester as TesterBase,
 )
 from calibre.utils.config import JSONConfig
 
diff --git a/src/calibre/gui2/custom_column_widgets.py b/src/calibre/gui2/custom_column_widgets.py
index 7969dbfe9d..243f30331e 100644
--- a/src/calibre/gui2/custom_column_widgets.py
+++ b/src/calibre/gui2/custom_column_widgets.py
@@ -8,24 +8,26 @@ __docformat__ = 'restructuredtext en'
 import os
 from collections import OrderedDict
 from functools import partial
-
-from qt.core import (Qt, QComboBox, QLabel, QSpinBox, QDoubleSpinBox,
-        QDateTime, QGroupBox, QVBoxLayout, QSizePolicy, QGridLayout, QUrl,
-        QSpacerItem, QIcon, QCheckBox, QWidget, QHBoxLayout, QLineEdit,
-        QMessageBox, QToolButton, QPlainTextEdit, QApplication, QStyle, QDialog)
+from qt.core import (
+    QApplication, QCheckBox, QComboBox, QDateTime, QDialog, QDoubleSpinBox, QGridLayout,
+    QGroupBox, QHBoxLayout, QIcon, QLabel, QLineEdit, QMessageBox, QPlainTextEdit,
+    QSizePolicy, QSpacerItem, QSpinBox, QStyle, Qt, QToolButton, QUrl, QVBoxLayout,
+    QWidget,
+)
 
 from calibre.ebooks.metadata import title_sort
-from calibre.utils.date import (qt_to_dt, now, as_local_time, as_utc,
-                                internal_iso_format_string, is_date_undefined)
-from calibre.gui2.complete2 import EditWithComplete as EWC
+from calibre.gui2 import UNDEFINED_QDATETIME, elided_text, error_dialog, gprefs
 from calibre.gui2.comments_editor import Editor as CommentsEditor
-from calibre.gui2 import UNDEFINED_QDATETIME, error_dialog, elided_text, gprefs
+from calibre.gui2.complete2 import EditWithComplete as EWC
 from calibre.gui2.dialogs.tag_editor import TagEditor
-from calibre.utils.config import tweaks
-from calibre.utils.icu import sort_key
-from calibre.library.comments import comments_to_html
 from calibre.gui2.library.delegates import ClearingDoubleSpinBox, ClearingSpinBox
-from calibre.gui2.widgets2 import RatingEditor, DateTimeEdit as DateTimeEditBase
+from calibre.gui2.widgets2 import DateTimeEdit as DateTimeEditBase, RatingEditor
+from calibre.library.comments import comments_to_html
+from calibre.utils.config import tweaks
+from calibre.utils.date import (
+    as_local_time, as_utc, internal_iso_format_string, is_date_undefined, now, qt_to_dt,
+)
+from calibre.utils.icu import lower as icu_lower, sort_key
 
 
 class EditWithComplete(EWC):
diff --git a/src/calibre/gui2/device_drivers/mtp_folder_browser.py b/src/calibre/gui2/device_drivers/mtp_folder_browser.py
index 3855b4f736..a852b6b83e 100644
--- a/src/calibre/gui2/device_drivers/mtp_folder_browser.py
+++ b/src/calibre/gui2/device_drivers/mtp_folder_browser.py
@@ -6,11 +6,13 @@ __copyright__ = '2012, Kovid Goyal <kovid at kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
 from operator import attrgetter
-
-from qt.core import (QTabWidget, QTreeWidget, QTreeWidgetItem, Qt, QDialog,
-        QDialogButtonBox, QVBoxLayout, QSize, pyqtSignal, QIcon, QLabel)
+from qt.core import (
+    QDialog, QDialogButtonBox, QIcon, QLabel, QSize, Qt, QTabWidget, QTreeWidget,
+    QTreeWidgetItem, QVBoxLayout, pyqtSignal,
+)
 
 from calibre.gui2 import file_icon_provider
+from calibre.utils.icu import lower as icu_lower
 
 
 def browser_item(f, parent):
diff --git a/src/calibre/gui2/dialogs/authors_edit.py b/src/calibre/gui2/dialogs/authors_edit.py
index 5777013d9a..2de105021c 100644
--- a/src/calibre/gui2/dialogs/authors_edit.py
+++ b/src/calibre/gui2/dialogs/authors_edit.py
@@ -5,15 +5,16 @@ __license__ = 'GPL v3'
 __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
 from collections import OrderedDict
-
 from qt.core import (
-    QDialog, QGridLayout, QDialogButtonBox, QListWidget, QApplication, Qt,
-    pyqtSignal, QSize, QPushButton, QIcon, QStyledItemDelegate, QLabel, QAbstractItemView)
+    QAbstractItemView, QApplication, QDialog, QDialogButtonBox, QGridLayout, QIcon,
+    QLabel, QListWidget, QPushButton, QSize, QStyledItemDelegate, Qt, pyqtSignal,
+)
 
-from calibre.utils.config_base import tweaks
+from calibre.ebooks.metadata import string_to_authors
 from calibre.gui2 import gprefs
 from calibre.gui2.complete2 import EditWithComplete
-from calibre.ebooks.metadata import string_to_authors
+from calibre.utils.config_base import tweaks
+from calibre.utils.icu import lower as icu_lower
 
 
 class ItemDelegate(QStyledItemDelegate):
diff --git a/src/calibre/gui2/dialogs/edit_authors_dialog.py b/src/calibre/gui2/dialogs/edit_authors_dialog.py
index 69a0907150..7f3dfb657b 100644
--- a/src/calibre/gui2/dialogs/edit_authors_dialog.py
+++ b/src/calibre/gui2/dialogs/edit_authors_dialog.py
@@ -5,19 +5,22 @@ __copyright__ = '2008, Kovid Goyal kovid@kovidgoyal.net'
 __docformat__ = 'restructuredtext en'
 __license__   = 'GPL v3'
 
-from functools import partial
 from contextlib import contextmanager
-
-from qt.core import (Qt, QDialog, QTableWidgetItem, QAbstractItemView, QIcon,
-                  QDialogButtonBox, QFrame, QLabel, QTimer, QMenu, QApplication,
-                  QItemDelegate, QAction)
+from functools import partial
+from qt.core import (
+    QAbstractItemView, QAction, QApplication, QDialog, QDialogButtonBox, QFrame, QIcon,
+    QItemDelegate, QLabel, QMenu, Qt, QTableWidgetItem, QTimer,
+)
 
 from calibre.ebooks.metadata import author_to_author_sort, string_to_authors
 from calibre.gui2 import error_dialog, gprefs
 from calibre.gui2.dialogs.edit_authors_dialog_ui import Ui_EditAuthorsDialog
 from calibre.utils.config import prefs
 from calibre.utils.config_base import tweaks
-from calibre.utils.icu import sort_key, primary_contains, contains, primary_startswith
+from calibre.utils.icu import (
+    contains, lower as icu_lower, primary_contains, primary_startswith, sort_key,
+    upper as icu_upper,
+)
 
 QT_HIDDEN_CLEAR_ACTION = '_q_qlineeditclearaction'
 
diff --git a/src/calibre/gui2/dialogs/metadata_bulk.py b/src/calibre/gui2/dialogs/metadata_bulk.py
index 2706c34906..1ff57fbd65 100644
--- a/src/calibre/gui2/dialogs/metadata_bulk.py
+++ b/src/calibre/gui2/dialogs/metadata_bulk.py
@@ -7,9 +7,9 @@ import regex
 from collections import defaultdict, namedtuple
 from io import BytesIO
 from qt.core import (
-    QApplication, QComboBox, QCompleter, QDateTime, QDialog,
-    QDialogButtonBox, QFont, QGridLayout, QInputDialog, QLabel, QLineEdit,
-    QProgressBar, QSize, Qt, QVBoxLayout, pyqtSignal
+    QApplication, QComboBox, QCompleter, QDateTime, QDialog, QDialogButtonBox, QFont,
+    QGridLayout, QInputDialog, QLabel, QLineEdit, QProgressBar, QSize, Qt, QVBoxLayout,
+    pyqtSignal,
 )
 from threading import Thread
 
@@ -21,7 +21,7 @@ from calibre.ebooks.metadata.book.formatter import SafeFormat
 from calibre.ebooks.metadata.opf2 import OPF
 from calibre.gui2 import (
     UNDEFINED_QDATETIME, FunctionDispatcher, error_dialog, gprefs, info_dialog,
-    question_dialog
+    question_dialog,
 )
 from calibre.gui2.custom_column_widgets import populate_metadata_page
 from calibre.gui2.dialogs.metadata_bulk_ui import Ui_MetadataBulkDialog
@@ -30,7 +30,9 @@ from calibre.gui2.dialogs.template_line_editor import TemplateLineEditor
 from calibre.gui2.widgets import LineEditECM
 from calibre.utils.config import JSONConfig, dynamic, prefs, tweaks
 from calibre.utils.date import internal_iso_format_string, qt_to_dt
-from calibre.utils.icu import capitalize, sort_key
+from calibre.utils.icu import (
+    capitalize, lower as icu_lower, sort_key, upper as icu_upper,
+)
 from calibre.utils.titlecase import titlecase
 from polyglot.builtins import error_message, iteritems, itervalues, native_string_type
 
@@ -317,7 +319,7 @@ class MyBlockingBusy(QDialog):  # {{{
         elif args.cover_action == 'trim':
             self.progress_next_step_range.emit(len(self.ids))
             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,
             )
             for book_id in self.ids:
                 cdata = cache.cover(book_id)
diff --git a/src/calibre/gui2/dialogs/plugin_updater.py b/src/calibre/gui2/dialogs/plugin_updater.py
index 7bd8c75fad..0fd4658189 100644
--- a/src/calibre/gui2/dialogs/plugin_updater.py
+++ b/src/calibre/gui2/dialogs/plugin_updater.py
@@ -9,24 +9,25 @@ import datetime
 import re
 import traceback
 from qt.core import (
-    QAbstractItemView, QAbstractTableModel, QAction, QBrush, QComboBox,
-    QDialog, QDialogButtonBox, QFont, QFrame, QHBoxLayout, QIcon, QLabel, QLineEdit,
-    QModelIndex, QSize, QSortFilterProxyModel, Qt, QTableView, QUrl, QVBoxLayout
+    QAbstractItemView, QAbstractTableModel, QAction, QBrush, QComboBox, QDialog,
+    QDialogButtonBox, QFont, QFrame, QHBoxLayout, QIcon, QLabel, QLineEdit, QModelIndex,
+    QSize, QSortFilterProxyModel, Qt, QTableView, QUrl, QVBoxLayout,
 )
 
 from calibre import prints
 from calibre.constants import (
-    DEBUG, __appname__, __version__, ismacos, iswindows, numeric_version
+    DEBUG, __appname__, __version__, ismacos, iswindows, numeric_version,
 )
 from calibre.customize import PluginInstallationType
 from calibre.customize.ui import (
     NameConflict, add_plugin, disable_plugin, enable_plugin, has_external_plugins,
-    initialized_plugins, is_disabled, remove_plugin
+    initialized_plugins, is_disabled, remove_plugin,
 )
 from calibre.gui2 import error_dialog, gprefs, info_dialog, open_url, question_dialog
 from calibre.gui2.preferences.plugins import ConfigWidget
 from calibre.utils.date import UNDEFINED_DATE, format_date
 from calibre.utils.https import get_https_resource_securely
+from calibre.utils.icu import lower as icu_lower
 from polyglot.builtins import itervalues
 
 SERVER = 'https://code.calibre-ebook.com/plugins/'
diff --git a/src/calibre/gui2/dialogs/saved_search_editor.py b/src/calibre/gui2/dialogs/saved_search_editor.py
index 20deb7072c..1a8b83274c 100644
--- a/src/calibre/gui2/dialogs/saved_search_editor.py
+++ b/src/calibre/gui2/dialogs/saved_search_editor.py
@@ -3,15 +3,15 @@
 
 
 from qt.core import (
-    QFormLayout, QIcon, QLabel, QLineEdit, QListWidget, Qt, QVBoxLayout, QDialog,
-    QDialogButtonBox, QPlainTextEdit
+    QDialog, QDialogButtonBox, QFormLayout, QIcon, QLabel, QLineEdit, QListWidget,
+    QPlainTextEdit, Qt, QVBoxLayout,
 )
 
 from calibre import prepare_string_for_xml
 from calibre.gui2 import error_dialog
 from calibre.gui2.dialogs.confirm_delete import confirm
 from calibre.gui2.widgets2 import Dialog
-from calibre.utils.icu import sort_key
+from calibre.utils.icu import lower as icu_lower, sort_key
 
 
 def commit_searches(searches):
diff --git a/src/calibre/gui2/dialogs/tag_categories.py b/src/calibre/gui2/dialogs/tag_categories.py
index 090421f94d..9df414d4c8 100644
--- a/src/calibre/gui2/dialogs/tag_categories.py
+++ b/src/calibre/gui2/dialogs/tag_categories.py
@@ -1,15 +1,16 @@
 __license__   = 'GPL v3'
 __copyright__ = '2008, Kovid Goyal <kovid at kovidgoyal.net>'
 
-from qt.core import (Qt, QApplication, QDialog, QIcon, QListWidgetItem)
-
 from collections import namedtuple
+from qt.core import QApplication, QDialog, QIcon, QListWidgetItem, Qt
 
 from calibre.constants import islinux
 from calibre.gui2 import error_dialog, warning_dialog
 from calibre.gui2.dialogs.confirm_delete import confirm
 from calibre.gui2.dialogs.tag_categories_ui import Ui_TagCategories
-from calibre.utils.icu import primary_sort_key, strcmp, primary_contains
+from calibre.utils.icu import (
+    lower as icu_lower, primary_contains, primary_sort_key, strcmp,
+)
 
 
 class TagCategories(QDialog, Ui_TagCategories):
diff --git a/src/calibre/gui2/dialogs/tag_list_editor.py b/src/calibre/gui2/dialogs/tag_list_editor.py
index be790b809b..a452b57391 100644
--- a/src/calibre/gui2/dialogs/tag_list_editor.py
+++ b/src/calibre/gui2/dialogs/tag_list_editor.py
@@ -3,19 +3,23 @@
 
 
 from functools import partial
+from qt.core import (
+    QAbstractItemView, QAction, QApplication, QColor, QDialog, QDialogButtonBox, QFrame,
+    QIcon, QItemDelegate, QLabel, QMenu, QSize, Qt, QTableWidgetItem, QTimer,
+    pyqtSignal,
+)
 
-from qt.core import (Qt, QDialog, QTableWidgetItem, QIcon, QSize, QAbstractItemView,
-                      QDialogButtonBox, QItemDelegate, QApplication,
-                      pyqtSignal, QAction, QFrame, QLabel, QTimer, QMenu, QColor)
-
+from calibre.gui2 import error_dialog, gprefs, question_dialog
 from calibre.gui2.actions.show_quickview import get_quickview_action_plugin
 from calibre.gui2.complete2 import EditWithComplete
-from calibre.gui2.dialogs.tag_list_editor_ui import Ui_TagListEditor
 from calibre.gui2.dialogs.confirm_delete import confirm
+from calibre.gui2.dialogs.tag_list_editor_ui import Ui_TagListEditor
 from calibre.gui2.widgets import EnLineEdit
-from calibre.gui2 import question_dialog, error_dialog, gprefs
 from calibre.utils.config import prefs
-from calibre.utils.icu import contains, primary_contains, primary_startswith, capitalize
+from calibre.utils.icu import (
+    capitalize, contains, lower as icu_lower, primary_contains, primary_startswith,
+    upper as icu_upper,
+)
 from calibre.utils.titlecase import titlecase
 
 QT_HIDDEN_CLEAR_ACTION = '_q_qlineeditclearaction'
diff --git a/src/calibre/gui2/dialogs/template_dialog.py b/src/calibre/gui2/dialogs/template_dialog.py
index 22086c705f..5077bb980f 100644
--- a/src/calibre/gui2/dialogs/template_dialog.py
+++ b/src/calibre/gui2/dialogs/template_dialog.py
@@ -32,7 +32,7 @@ from calibre.utils.config_base import tweaks
 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 sort_key
+from calibre.utils.icu import lower as icu_lower, sort_key
 from calibre.utils.localization import localize_user_manual_link
 from calibre.utils.resources import get_path as P
 
diff --git a/src/calibre/gui2/font_family_chooser.py b/src/calibre/gui2/font_family_chooser.py
index 5de96c6e6a..338828d9b7 100644
--- a/src/calibre/gui2/font_family_chooser.py
+++ b/src/calibre/gui2/font_family_chooser.py
@@ -8,14 +8,15 @@ __docformat__ = 'restructuredtext en'
 import os
 import shutil
 from qt.core import (
-    QAbstractItemView, QDialog, QDialogButtonBox, QFont, QFontComboBox,
-    QFontDatabase, QFontInfo, QFontMetrics, QGridLayout, QHBoxLayout, QIcon, QLabel,
-    QLineEdit, QListView, QPen, QPushButton, QSize, QSizePolicy, QStringListModel,
-    QStyle, QStyledItemDelegate, Qt, QToolButton, QVBoxLayout, QWidget, pyqtSignal
+    QAbstractItemView, QDialog, QDialogButtonBox, QFont, QFontComboBox, QFontDatabase,
+    QFontInfo, QFontMetrics, QGridLayout, QHBoxLayout, QIcon, QLabel, QLineEdit,
+    QListView, QPen, QPushButton, QSize, QSizePolicy, QStringListModel, QStyle,
+    QStyledItemDelegate, Qt, QToolButton, QVBoxLayout, QWidget, pyqtSignal,
 )
 
 from calibre.constants import config_dir
 from calibre.gui2 import choose_files, empty_index, error_dialog, info_dialog
+from calibre.utils.icu import lower as icu_lower
 
 
 def add_fonts(parent):
diff --git a/src/calibre/gui2/metadata/diff.py b/src/calibre/gui2/metadata/diff.py
index c59ddeeee4..e12e283b5e 100644
--- a/src/calibre/gui2/metadata/diff.py
+++ b/src/calibre/gui2/metadata/diff.py
@@ -12,7 +12,7 @@ from qt.core import (
     QAction, QApplication, QCheckBox, QColor, QDialog, QDialogButtonBox, QFont,
     QGridLayout, QHBoxLayout, QIcon, QKeySequence, QLabel, QMenu, QPainter, QPen,
     QPixmap, QScrollArea, QSize, QSizePolicy, QStackedLayout, Qt, QToolButton,
-    QVBoxLayout, QWidget, pyqtSignal
+    QVBoxLayout, QWidget, pyqtSignal,
 )
 
 from calibre import fit_image
@@ -26,6 +26,7 @@ from calibre.gui2.metadata.basic_widgets import PubdateEdit, RatingEdit
 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 polyglot.builtins import iteritems, itervalues
 
 Widgets = namedtuple('Widgets', 'new old label button')
@@ -783,6 +784,7 @@ if __name__ == '__main__':
     ids = sorted(db.all_ids(), reverse=True)
     ids = tuple(zip(ids[0::2], ids[1::2]))
     gm = partial(db.get_metadata, index_is_id=True, get_cover=True, cover_as_data=True)
+
     def get_metadata(x):
         return list(map(gm, ids[x]))
     d = CompareMany(list(range(len(ids))), get_metadata, db.field_metadata, db=db)
diff --git a/src/calibre/gui2/preferences/search.py b/src/calibre/gui2/preferences/search.py
index 13faccb23f..d0264dfd2c 100644
--- a/src/calibre/gui2/preferences/search.py
+++ b/src/calibre/gui2/preferences/search.py
@@ -8,13 +8,14 @@ __docformat__ = 'restructuredtext en'
 from qt.core import QApplication, QTimer
 
 from calibre.db.categories import find_categories
-from calibre.gui2.preferences import ConfigWidgetBase, test_widget, \
-        CommaSeparatedList, AbortCommit
-from calibre.gui2.preferences.search_ui import Ui_Form
 from calibre.gui2 import config, error_dialog, gprefs
-from calibre.utils.config import prefs
-from calibre.utils.icu import sort_key
+from calibre.gui2.preferences import (
+    AbortCommit, CommaSeparatedList, ConfigWidgetBase, test_widget,
+)
+from calibre.gui2.preferences.search_ui import Ui_Form
 from calibre.library.caches import set_use_primary_find_in_search
+from calibre.utils.config import prefs
+from calibre.utils.icu import lower as icu_lower, sort_key
 from polyglot.builtins import iteritems
 
 
diff --git a/src/calibre/gui2/store/search/models.py b/src/calibre/gui2/store/search/models.py
index ed63c66e27..9e14375134 100644
--- a/src/calibre/gui2/store/search/models.py
+++ b/src/calibre/gui2/store/search/models.py
@@ -2,18 +2,19 @@ __license__ = 'GPL 3'
 __copyright__ = '2011, John Schember <john@nachtimwald.com>'
 __docformat__ = 'restructuredtext en'
 
-import re, string
+import re
+import string
 from operator import attrgetter
-
-from qt.core import (Qt, QAbstractItemModel, QPixmap, QModelIndex, QSize,
-                      pyqtSignal, QIcon, QApplication)
+from qt.core import (
+    QAbstractItemModel, QApplication, QIcon, QModelIndex, QPixmap, QSize, Qt,
+    pyqtSignal,
+)
 
 from calibre import force_unicode
 from calibre.gui2 import FunctionDispatcher
+from calibre.gui2.store.search.download_thread import CoverThreadPool, DetailsThreadPool
 from calibre.gui2.store.search_result import SearchResult
-from calibre.gui2.store.search.download_thread import DetailsThreadPool, \
-    CoverThreadPool
-from calibre.utils.icu import sort_key
+from calibre.utils.icu import lower as icu_lower, sort_key
 from calibre.utils.localization import pgettext
 from calibre.utils.search_query_parser import SearchQueryParser
 
diff --git a/src/calibre/gui2/tag_browser/model.py b/src/calibre/gui2/tag_browser/model.py
index c16cb0988d..34b20627af 100644
--- a/src/calibre/gui2/tag_browser/model.py
+++ b/src/calibre/gui2/tag_browser/model.py
@@ -10,21 +10,22 @@ import os
 import traceback
 from collections import OrderedDict, namedtuple
 from qt.core import (
-    QAbstractItemModel, QFont, QIcon, QMimeData, QModelIndex, QObject, Qt,
-    pyqtSignal
+    QAbstractItemModel, QFont, QIcon, QMimeData, QModelIndex, QObject, Qt, pyqtSignal,
 )
 
 from calibre.constants import config_dir
 from calibre.db.categories import Tag, category_display_order
 from calibre.ebooks.metadata import rating_to_stars
-from calibre.gui2 import config, error_dialog, file_icon_provider, gprefs, question_dialog
+from calibre.gui2 import (
+    config, error_dialog, file_icon_provider, gprefs, question_dialog,
+)
 from calibre.gui2.dialogs.confirm_delete import confirm
 from calibre.library.field_metadata import category_icon_map
 from calibre.utils.config import prefs, tweaks
 from calibre.utils.formatter import EvalFormatter
 from calibre.utils.icu import (
-    contains, lower, primary_contains, primary_strcmp, sort_key,
-    strcmp, collation_order_for_partitioning
+    collation_order_for_partitioning, contains, lower, lower as icu_lower,
+    primary_contains, primary_strcmp, sort_key, strcmp, upper as icu_upper,
 )
 from calibre.utils.serialize import json_dumps, json_loads
 from polyglot.builtins import iteritems, itervalues
diff --git a/src/calibre/gui2/tag_mapper.py b/src/calibre/gui2/tag_mapper.py
index a4266e93fa..0f11a3fd03 100644
--- a/src/calibre/gui2/tag_mapper.py
+++ b/src/calibre/gui2/tag_mapper.py
@@ -6,9 +6,9 @@ import textwrap
 from collections import OrderedDict
 from qt.core import (
     QAbstractItemView, QComboBox, QDialog, QDialogButtonBox, QHBoxLayout, QIcon,
-    QInputDialog, QItemSelectionModel, QLabel, QLineEdit, QListWidget,
-    QListWidgetItem, QMenu, QPalette, QPushButton, QSize, QStaticText, QStyle,
-    QStyledItemDelegate, Qt, QToolButton, QVBoxLayout, QWidget, pyqtSignal
+    QInputDialog, QItemSelectionModel, QLabel, QLineEdit, QListWidget, QListWidgetItem,
+    QMenu, QPalette, QPushButton, QSize, QStaticText, QStyle, QStyledItemDelegate, Qt,
+    QToolButton, QVBoxLayout, QWidget, pyqtSignal,
 )
 
 from calibre.ebooks.metadata.tag_mapper import compile_pat, map_tags
diff --git a/src/calibre/gui2/toc/main.py b/src/calibre/gui2/toc/main.py
index 5111a36399..50f1e6565b 100644
--- a/src/calibre/gui2/toc/main.py
+++ b/src/calibre/gui2/toc/main.py
@@ -8,11 +8,10 @@ import tempfile
 import textwrap
 from functools import partial
 from qt.core import (
-    QAbstractItemView, QCheckBox, QCursor, QDialog, QDialogButtonBox,
-    QEvent, QFrame, QGridLayout, QIcon, QInputDialog, QItemSelectionModel,
-    QKeySequence, QLabel, QMenu, QPushButton, QScrollArea, QSize, QSizePolicy,
-    QStackedWidget, Qt, QToolButton, QTreeWidget, QTreeWidgetItem, QVBoxLayout,
-    QWidget, pyqtSignal
+    QAbstractItemView, QCheckBox, QCursor, QDialog, QDialogButtonBox, QEvent, QFrame,
+    QGridLayout, QIcon, QInputDialog, QItemSelectionModel, QKeySequence, QLabel, QMenu,
+    QPushButton, QScrollArea, QSize, QSizePolicy, QStackedWidget, Qt, QToolButton,
+    QTreeWidget, QTreeWidgetItem, QVBoxLayout, QWidget, pyqtSignal,
 )
 from threading import Thread
 from time import monotonic
@@ -20,17 +19,16 @@ from time import monotonic
 from calibre.constants import TOC_DIALOG_APP_UID, islinux, iswindows
 from calibre.ebooks.oeb.polish.container import AZW3Container, get_container
 from calibre.ebooks.oeb.polish.toc import (
-    TOC, add_id, commit_toc, from_files, from_links, from_xpaths, get_toc
-)
-from calibre.gui2 import (
-    Application, error_dialog, info_dialog, set_app_uid
+    TOC, add_id, commit_toc, from_files, from_links, from_xpaths, get_toc,
 )
+from calibre.gui2 import Application, error_dialog, info_dialog, set_app_uid
 from calibre.gui2.convert.xpath_wizard import XPathEdit
 from calibre.gui2.progress_indicator import ProgressIndicator
 from calibre.gui2.toc.location import ItemEdit
 from calibre.ptempfile import reset_base_dir
 from calibre.utils.config import JSONConfig
 from calibre.utils.filenames import atomic_rename
+from calibre.utils.icu import lower as icu_lower, upper as icu_upper
 from calibre.utils.logging import GUILog
 
 ICON_SIZE = 24
@@ -1166,6 +1164,7 @@ class TOCEditor(QDialog):  # {{{
 def main(shm_name=None):
     import json
     import struct
+
     from calibre.utils.shm import SharedMemory
 
     # Ensure we can continue to function if GUI is closed
diff --git a/src/calibre/gui2/tweak_book/manage_fonts.py b/src/calibre/gui2/tweak_book/manage_fonts.py
index a6ee741f84..14cfaaa032 100644
--- a/src/calibre/gui2/tweak_book/manage_fonts.py
+++ b/src/calibre/gui2/tweak_book/manage_fonts.py
@@ -4,23 +4,24 @@
 __license__ = 'GPL v3'
 __copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'
 
-import sys, textwrap
+import sys
+import textwrap
 from io import BytesIO
-
 from qt.core import (
-    QSplitter, QVBoxLayout, QTableView, QWidget, QLabel, QAbstractTableModel,
-    Qt, QTimer, QPushButton, pyqtSignal, QFormLayout, QLineEdit, QIcon, QSize,
-    QHBoxLayout, QTextEdit, QApplication, QMessageBox, QAbstractItemView, QDialog, QDialogButtonBox)
+    QAbstractItemView, QAbstractTableModel, QApplication, QDialog, QDialogButtonBox,
+    QFormLayout, QHBoxLayout, QIcon, QLabel, QLineEdit, QMessageBox, QPushButton, QSize,
+    QSplitter, Qt, QTableView, QTextEdit, QTimer, QVBoxLayout, QWidget, pyqtSignal,
+)
 
 from calibre.ebooks.oeb.polish.container import get_container
-from calibre.ebooks.oeb.polish.fonts import font_family_data, change_font
+from calibre.ebooks.oeb.polish.fonts import change_font, font_family_data
 from calibre.gui2 import error_dialog, info_dialog
 from calibre.gui2.tweak_book import current_container, set_current_container
 from calibre.gui2.tweak_book.widgets import Dialog
 from calibre.gui2.widgets import BusyCursor
-from calibre.utils.icu import primary_sort_key as sort_key
-from calibre.utils.fonts.scanner import font_scanner, NoFonts
 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 polyglot.builtins import iteritems
 
 
diff --git a/src/calibre/library/caches.py b/src/calibre/library/caches.py
index 197cc736f8..efc3994a1d 100644
--- a/src/calibre/library/caches.py
+++ b/src/calibre/library/caches.py
@@ -5,22 +5,24 @@ __license__   = 'GPL v3'
 __copyright__ = '2010, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-import time, traceback, locale
-from itertools import repeat
-from datetime import timedelta
-from threading import Thread
+import locale
+import time
+import traceback
 from contextlib import suppress
+from datetime import timedelta
+from itertools import repeat
+from threading import Thread
 
-from calibre.utils.config import tweaks, prefs
-from calibre.utils.date import parse_date, now, UNDEFINED_DATE, clean_date_for_sort
-from calibre.utils.search_query_parser import SearchQueryParser
-from calibre.utils.search_query_parser import ParseException
-from calibre.utils.localization import (canonicalize_lang, lang_map, get_udc)
+from calibre import force_unicode, prints
 from calibre.db.search import CONTAINS_MATCH, EQUALS_MATCH, REGEXP_MATCH, _match
-from calibre.ebooks.metadata import title_sort, author_to_author_sort
+from calibre.ebooks.metadata import author_to_author_sort, title_sort
 from calibre.ebooks.metadata.opf2 import metadata_to_opf
-from calibre import prints, force_unicode
-from polyglot.builtins import iteritems, itervalues, string_or_bytes, cmp
+from calibre.utils.config import prefs, tweaks
+from calibre.utils.date import UNDEFINED_DATE, clean_date_for_sort, now, parse_date
+from calibre.utils.icu import lower as icu_lower
+from calibre.utils.localization import canonicalize_lang, get_udc, lang_map
+from calibre.utils.search_query_parser import ParseException, SearchQueryParser
+from polyglot.builtins import cmp, iteritems, itervalues, string_or_bytes
 
 
 class MetadataBackup(Thread):  # {{{
@@ -437,6 +439,7 @@ class ResultCache(SearchQueryParser):  # {{{
 
         if val_func is None:
             loc = self.field_metadata[location]['rec_index']
+
             def val_func(item, loc=loc):
                 return item[loc]
         q = ''
@@ -472,6 +475,7 @@ class ResultCache(SearchQueryParser):  # {{{
             elif dt == 'rating':
                 def cast(x):
                     return (0 if x is None else int(x))
+
                 def adjust(x):
                     return (x // 2)
             elif dt in ('float', 'composite'):
diff --git a/src/calibre/library/catalogs/epub_mobi_builder.py b/src/calibre/library/catalogs/epub_mobi_builder.py
index cabe14deab..79a6964821 100644
--- a/src/calibre/library/catalogs/epub_mobi_builder.py
+++ b/src/calibre/library/catalogs/epub_mobi_builder.py
@@ -35,7 +35,7 @@ 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
+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.resources import get_image_path as I, get_path as P
 from calibre.utils.xml_parse import safe_xml_fromstring
diff --git a/src/calibre/library/database2.py b/src/calibre/library/database2.py
index 268258a21a..3ea0ecb429 100644
--- a/src/calibre/library/database2.py
+++ b/src/calibre/library/database2.py
@@ -58,7 +58,7 @@ from calibre.utils.filenames import (
     WindowsAtomicFolderMove, ascii_filename, hardlink_file, samefile,
 )
 from calibre.utils.formatter_functions import load_user_template_functions
-from calibre.utils.icu import lower, sort_key, strcmp
+from calibre.utils.icu import lower, lower as icu_lower, sort_key, strcmp
 from calibre.utils.img import save_cover_data_to
 from calibre.utils.localization import calibre_langcode_to_name, canonicalize_lang
 from calibre.utils.recycle_bin import delete_file, delete_tree
diff --git a/src/calibre/library/field_metadata.py b/src/calibre/library/field_metadata.py
index be54e3f652..f1efea9a9f 100644
--- a/src/calibre/library/field_metadata.py
+++ b/src/calibre/library/field_metadata.py
@@ -8,6 +8,7 @@ import traceback
 from collections import OrderedDict
 
 from calibre.utils.config_base import tweaks
+from calibre.utils.icu import lower as icu_lower
 from polyglot.builtins import iteritems, itervalues
 
 category_icon_map = {
diff --git a/src/calibre/srv/metadata.py b/src/calibre/srv/metadata.py
index 6960b89d8f..8f3dabb16a 100644
--- a/src/calibre/srv/metadata.py
+++ b/src/calibre/srv/metadata.py
@@ -3,8 +3,8 @@
 
 
 import os
-from copy import copy
 from collections import namedtuple
+from copy import copy
 from datetime import datetime, time
 from functools import partial
 from threading import Lock
@@ -12,14 +12,14 @@ from threading import Lock
 from calibre.constants import config_dir
 from calibre.db.categories import Tag, category_display_order
 from calibre.ebooks.metadata.sources.identify import urls_from_identifiers
-from calibre.utils.date import isoformat, UNDEFINED_DATE, local_tz
-from calibre.utils.config import tweaks
-from calibre.utils.formatter import EvalFormatter
-from calibre.utils.file_type_icons import EXT_MAP
-from calibre.utils.icu import collation_order_for_partitioning
-from calibre.utils.localization import calibre_langcode_to_name
 from calibre.library.comments import comments_to_html, markdown
 from calibre.library.field_metadata import category_icon_map
+from calibre.utils.config import tweaks
+from calibre.utils.date import UNDEFINED_DATE, isoformat, local_tz
+from calibre.utils.file_type_icons import EXT_MAP
+from calibre.utils.formatter import EvalFormatter
+from calibre.utils.icu import collation_order_for_partitioning, upper as icu_upper
+from calibre.utils.localization import calibre_langcode_to_name
 from polyglot.builtins import iteritems, itervalues
 from polyglot.urllib import quote
 
diff --git a/src/calibre/utils/fonts/scanner.py b/src/calibre/utils/fonts/scanner.py
index d3b2983308..c1985250e2 100644
--- a/src/calibre/utils/fonts/scanner.py
+++ b/src/calibre/utils/fonts/scanner.py
@@ -14,7 +14,7 @@ from calibre.constants import (
     DEBUG, config_dir, filesystem_encoding, ismacos, iswindows, isworker,
 )
 from calibre.utils.fonts.metadata import FontMetadata, UnsupportedFont
-from calibre.utils.icu import sort_key
+from calibre.utils.icu import lower as icu_lower, sort_key
 from calibre.utils.resources import get_path as P
 from polyglot.builtins import itervalues
 
diff --git a/src/calibre/utils/formatter_functions.py b/src/calibre/utils/formatter_functions.py
index ed7c86b086..30540ca2d4 100644
--- a/src/calibre/utils/formatter_functions.py
+++ b/src/calibre/utils/formatter_functions.py
@@ -26,7 +26,7 @@ from calibre.constants import DEBUG
 from calibre.ebooks.metadata import title_sort
 from calibre.utils.config import tweaks
 from calibre.utils.date import UNDEFINED_DATE, format_date, now, parse_date
-from calibre.utils.icu import capitalize, sort_key, strcmp
+from calibre.utils.icu import capitalize, lower as icu_lower, sort_key, strcmp
 from calibre.utils.localization import _, calibre_langcode_to_name, canonicalize_lang
 from calibre.utils.titlecase import titlecase
 from polyglot.builtins import iteritems, itervalues
diff --git a/src/calibre/utils/icu.py b/src/calibre/utils/icu.py
index 6ee1c4ed8a..596adfee46 100644
--- a/src/calibre/utils/icu.py
+++ b/src/calibre/utils/icu.py
@@ -287,7 +287,7 @@ def partition_by_first_letter(items, reverse=False, key=lambda x:x):
     ans = OrderedDict()
     last_c, last_ordnum = ' ', 0
     for item in items:
-        c = icu_upper(key(item) or ' ')
+        c = upper(key(item) or ' ')
         ordnum, ordlen = collation_order(c)
         if last_ordnum != ordnum:
             last_c = c[0:1]
diff --git a/src/calibre/utils/matcher.py b/src/calibre/utils/matcher.py
index 07f1c799d0..aac31436e0 100644
--- a/src/calibre/utils/matcher.py
+++ b/src/calibre/utils/matcher.py
@@ -4,17 +4,22 @@
 __license__ = 'GPL v3'
 __copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'
 
-import atexit, os, sys
-from math import ceil
-from unicodedata import normalize
-from threading import Thread, Lock
-from operator import itemgetter
+import atexit
+import os
+import sys
 from collections import OrderedDict
 from itertools import islice
+from math import ceil
+from operator import itemgetter
+from threading import Lock, Thread
+from unicodedata import normalize
 
-from calibre import detect_ncpus as cpu_count, as_unicode
+from calibre import as_unicode, detect_ncpus as cpu_count
 from calibre.constants import filesystem_encoding
-from calibre.utils.icu import primary_sort_key, primary_find, primary_collator
+from calibre.utils.icu import (
+    lower as icu_lower, primary_collator, primary_find, primary_sort_key,
+    upper as icu_upper,
+)
 from polyglot.builtins import iteritems, itervalues
 from polyglot.queue import Queue
 
@@ -275,6 +280,7 @@ def test(return_tests=False):
         @unittest.skipIf(is_sanitized, 'Sanitizer enabled can\'t check for leaks')
         def test_mem_leaks(self):
             import gc
+
             from calibre.utils.mem import get_memory as memory
             m = Matcher(['a'], scorer=CScorer)
             m('a')