diff --git a/src/calibre/gui2/actions/choose_library.py b/src/calibre/gui2/actions/choose_library.py
index e68fe447f9..46f5025eb3 100644
--- a/src/calibre/gui2/actions/choose_library.py
+++ b/src/calibre/gui2/actions/choose_library.py
@@ -26,6 +26,7 @@ from calibre.gui2 import (
 )
 from calibre.gui2.actions import InterfaceAction
 from calibre.library import current_library_name
+from calibre.startup import connect_lambda
 from calibre.utils.config import prefs, tweaks
 from calibre.utils.icu import sort_key
 from calibre.utils.localization import ngettext
diff --git a/src/calibre/gui2/actions/copy_to_library.py b/src/calibre/gui2/actions/copy_to_library.py
index fbbbf92ad8..6890459fc1 100644
--- a/src/calibre/gui2/actions/copy_to_library.py
+++ b/src/calibre/gui2/actions/copy_to_library.py
@@ -26,6 +26,7 @@ from calibre.gui2.actions import InterfaceAction
 from calibre.gui2.actions.choose_library import library_qicon
 from calibre.gui2.dialogs.progress import ProgressDialog
 from calibre.gui2.widgets2 import Dialog
+from calibre.startup import connect_lambda
 from calibre.utils.config import prefs
 from calibre.utils.icu import numeric_sort_key, sort_key
 from calibre.utils.localization import ngettext
diff --git a/src/calibre/gui2/actions/device.py b/src/calibre/gui2/actions/device.py
index 665c9b91c5..2921b1d8e2 100644
--- a/src/calibre/gui2/actions/device.py
+++ b/src/calibre/gui2/actions/device.py
@@ -5,11 +5,12 @@ __license__   = 'GPL v3'
 __copyright__ = '2010, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-from qt.core import QIcon, QMenu, QTimer, QToolButton, pyqtSignal, QUrl
+from qt.core import QIcon, QMenu, QTimer, QToolButton, QUrl, pyqtSignal
 
-from calibre.gui2 import info_dialog, question_dialog, open_url
+from calibre.gui2 import info_dialog, open_url, question_dialog
 from calibre.gui2.actions import InterfaceAction
 from calibre.gui2.dialogs.smartdevice import SmartdeviceDialog
+from calibre.startup import connect_lambda
 from calibre.utils.icu import primary_sort_key
 from calibre.utils.smtp import config as email_config
 
diff --git a/src/calibre/gui2/actions/mark_books.py b/src/calibre/gui2/actions/mark_books.py
index a1abe17174..619fffcf9d 100644
--- a/src/calibre/gui2/actions/mark_books.py
+++ b/src/calibre/gui2/actions/mark_books.py
@@ -5,13 +5,15 @@ __license__ = 'GPL v3'
 __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
 from functools import partial
-
-from qt.core import (QTimer, QApplication, Qt, QEvent, QDialog, QMenu, QIcon,
-                     QDialogButtonBox, QPushButton, QLabel, QGridLayout)
+from qt.core import (
+    QApplication, QDialog, QDialogButtonBox, QEvent, QGridLayout, QIcon, QLabel, QMenu,
+    QPushButton, Qt, QTimer,
+)
 
 from calibre.gui2 import error_dialog
 from calibre.gui2.actions import InterfaceAction
 from calibre.gui2.widgets2 import HistoryComboBox
+from calibre.startup import connect_lambda
 from calibre.utils.icu import sort_key
 
 
diff --git a/src/calibre/gui2/actions/polish.py b/src/calibre/gui2/actions/polish.py
index 944978339f..2832c94679 100644
--- a/src/calibre/gui2/actions/polish.py
+++ b/src/calibre/gui2/actions/polish.py
@@ -22,6 +22,7 @@ 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.startup import connect_lambda
 from calibre.utils.config_base import tweaks
 from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems, itervalues
diff --git a/src/calibre/gui2/actions/similar_books.py b/src/calibre/gui2/actions/similar_books.py
index cac3aa2fe6..3d74bb6068 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.startup import connect_lambda
 from calibre.utils.icu import lower as icu_lower
 from polyglot.builtins import string_or_bytes
 
diff --git a/src/calibre/gui2/actions/toc_edit.py b/src/calibre/gui2/actions/toc_edit.py
index d077ed8d83..3ff9503c15 100644
--- a/src/calibre/gui2/actions/toc_edit.py
+++ b/src/calibre/gui2/actions/toc_edit.py
@@ -6,14 +6,15 @@ __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
 import os
-from itertools import count
 from collections import OrderedDict
+from itertools import count
 from qt.core import (
-    QCheckBox, QDialog, QDialogButtonBox, QGridLayout, QIcon, QLabel, QTimer
+    QCheckBox, QDialog, QDialogButtonBox, QGridLayout, QIcon, QLabel, QTimer,
 )
 
 from calibre.gui2 import error_dialog, gprefs, question_dialog
 from calibre.gui2.actions import InterfaceAction
+from calibre.startup import connect_lambda
 from calibre.utils.monotonic import monotonic
 from polyglot.builtins import iteritems
 
@@ -148,7 +149,10 @@ class ToCEditAction(InterfaceAction):
                 self.do_one(book_id, fmt)
 
     def do_one(self, book_id, fmt):
-        import struct, json, atexit
+        import atexit
+        import json
+        import struct
+
         from calibre.utils.shm import SharedMemory
         db = self.gui.current_db
         path = db.format(book_id, fmt, index_is_id=True, as_path=True)
diff --git a/src/calibre/gui2/actions/tweak_epub.py b/src/calibre/gui2/actions/tweak_epub.py
index dfa20b5452..05d2cc943c 100644
--- a/src/calibre/gui2/actions/tweak_epub.py
+++ b/src/calibre/gui2/actions/tweak_epub.py
@@ -6,11 +6,13 @@ __copyright__ = '2010, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
 import time
-
-from qt.core import QTimer, QDialog, QDialogButtonBox, QCheckBox, QVBoxLayout, QLabel, Qt
+from qt.core import (
+    QCheckBox, QDialog, QDialogButtonBox, QLabel, Qt, QTimer, QVBoxLayout,
+)
 
 from calibre.gui2 import error_dialog, question_dialog
 from calibre.gui2.actions import InterfaceAction
+from calibre.startup import connect_lambda
 
 
 class Choose(QDialog):
diff --git a/src/calibre/gui2/book_details.py b/src/calibre/gui2/book_details.py
index b085f4f9dd..fc38d86d41 100644
--- a/src/calibre/gui2/book_details.py
+++ b/src/calibre/gui2/book_details.py
@@ -30,6 +30,7 @@ from calibre.gui2.dnd import (
     dnd_get_files, dnd_get_image, dnd_has_extension, dnd_has_image, image_extensions,
 )
 from calibre.gui2.widgets2 import HTMLDisplay
+from calibre.startup import connect_lambda
 from calibre.utils.config import tweaks
 from calibre.utils.img import blend_image, image_from_x
 from calibre.utils.localization import is_rtl, langnames_to_langcodes
diff --git a/src/calibre/gui2/comments_editor.py b/src/calibre/gui2/comments_editor.py
index 0bd714957d..d69d2b59d7 100644
--- a/src/calibre/gui2/comments_editor.py
+++ b/src/calibre/gui2/comments_editor.py
@@ -10,23 +10,24 @@ from contextlib import contextmanager
 from html5_parser import parse
 from lxml import html
 from qt.core import (
-    QAction, QApplication, QBrush, QByteArray, QCheckBox, QColor, QColorDialog,
-    QDialog, QDialogButtonBox, QFont, QFontInfo, QFontMetrics, QFormLayout, QIcon,
-    QKeySequence, QLabel, QLineEdit, QMenu, QPalette, QPlainTextEdit, QPushButton,
-    QSize, QSyntaxHighlighter, Qt, QTabWidget, QTextBlockFormat, QTextCharFormat,
-    QTextCursor, QTextEdit, QTextFormat, QTextListFormat, QTimer, QToolButton, QUrl,
-    QVBoxLayout, QWidget, pyqtSignal, pyqtSlot
+    QAction, QApplication, QBrush, QByteArray, QCheckBox, QColor, QColorDialog, QDialog,
+    QDialogButtonBox, QFont, QFontInfo, QFontMetrics, QFormLayout, QIcon, QKeySequence,
+    QLabel, QLineEdit, QMenu, QPalette, QPlainTextEdit, QPushButton, QSize,
+    QSyntaxHighlighter, Qt, QTabWidget, QTextBlockFormat, QTextCharFormat, QTextCursor,
+    QTextEdit, QTextFormat, QTextListFormat, QTimer, QToolButton, QUrl, QVBoxLayout,
+    QWidget, pyqtSignal, pyqtSlot,
 )
 
 from calibre import xml_replace_entities
 from calibre.ebooks.chardet import xml_to_unicode
 from calibre.gui2 import (
-    NO_URL_FORMATTING, choose_files, error_dialog, gprefs, is_dark_theme
+    NO_URL_FORMATTING, choose_files, error_dialog, gprefs, is_dark_theme,
 )
 from calibre.gui2.book_details import css
 from calibre.gui2.flow_toolbar import create_flow_toolbar
 from calibre.gui2.widgets import LineEditECM
 from calibre.gui2.widgets2 import to_plain_text
+from calibre.startup import connect_lambda
 from calibre.utils.cleantext import clean_xml_chars
 from calibre.utils.config import tweaks
 from calibre.utils.imghdr import what
diff --git a/src/calibre/gui2/convert/look_and_feel.py b/src/calibre/gui2/convert/look_and_feel.py
index 0fcd6e6d3e..a3ea165681 100644
--- a/src/calibre/gui2/convert/look_and_feel.py
+++ b/src/calibre/gui2/convert/look_and_feel.py
@@ -6,12 +6,12 @@ __copyright__ = '2009, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
 import json
+from qt.core import QDialog, Qt
 
-from qt.core import Qt, QDialog
-
-from calibre.gui2.convert.look_and_feel_ui import Ui_Form
-from calibre.gui2.convert import Widget
 from calibre.ebooks.conversion.config import OPTIONS
+from calibre.gui2.convert import Widget
+from calibre.gui2.convert.look_and_feel_ui import Ui_Form
+from calibre.startup import connect_lambda
 from polyglot.builtins import iteritems
 
 
diff --git a/src/calibre/gui2/covers.py b/src/calibre/gui2/covers.py
index aa149041e8..7dbb2ccabb 100644
--- a/src/calibre/gui2/covers.py
+++ b/src/calibre/gui2/covers.py
@@ -6,19 +6,19 @@ from collections import OrderedDict
 from contextlib import suppress
 from copy import deepcopy
 from qt.core import (
-    QCheckBox, QColor, QColorDialog, QDialog, QDialogButtonBox,
-    QFormLayout, QFrame, QGridLayout, QHBoxLayout, QIcon, QInputDialog, QLabel,
-    QLineEdit, QListWidget, QListWidgetItem, QMenu, QPixmap, QPushButton, QSize,
-    QSizePolicy, QSpinBox, Qt, QTabWidget, QTimer, QToolButton, QVBoxLayout, QWidget,
-    pyqtSignal
+    QCheckBox, QColor, QColorDialog, QDialog, QDialogButtonBox, QFormLayout, QFrame,
+    QGridLayout, QHBoxLayout, QIcon, QInputDialog, QLabel, QLineEdit, QListWidget,
+    QListWidgetItem, QMenu, QPixmap, QPushButton, QSize, QSizePolicy, QSpinBox, Qt,
+    QTabWidget, QTimer, QToolButton, QVBoxLayout, QWidget, pyqtSignal,
 )
 
 from calibre.constants import config_dir
 from calibre.ebooks.covers import (
-    all_styles, cprefs, default_color_themes, generate_cover, override_prefs
+    all_styles, cprefs, default_color_themes, generate_cover, override_prefs,
 )
 from calibre.gui2 import error_dialog, gprefs
 from calibre.gui2.font_family_chooser import FontFamilyChooser
+from calibre.startup import connect_lambda
 from calibre.utils.date import now
 from calibre.utils.filenames import make_long_path_useable
 from calibre.utils.icu import primary_sort_key, sort_key
diff --git a/src/calibre/gui2/device.py b/src/calibre/gui2/device.py
index a9da487129..e1a6db40c3 100644
--- a/src/calibre/gui2/device.py
+++ b/src/calibre/gui2/device.py
@@ -43,6 +43,7 @@ from calibre.library.save_to_disk import find_plugboard
 from calibre.ptempfile import (
     PersistentTemporaryFile, force_unicode as filename_to_unicode,
 )
+from calibre.startup import connect_lambda
 from calibre.utils.config import device_prefs, tweaks
 from calibre.utils.filenames import ascii_filename
 from calibre.utils.img import scale_image
diff --git a/src/calibre/gui2/dialogs/book_info.py b/src/calibre/gui2/dialogs/book_info.py
index f6e31e6455..19ed838c92 100644
--- a/src/calibre/gui2/dialogs/book_info.py
+++ b/src/calibre/gui2/dialogs/book_info.py
@@ -4,21 +4,21 @@
 
 import textwrap
 from qt.core import (
-    QAction, QApplication, QBrush, QCheckBox, QDialog, QGridLayout,
-    QHBoxLayout, QIcon, QKeySequence, QLabel, QListView, QModelIndex, QPalette,
-    QPixmap, QPushButton, QShortcut, QSize, Qt, QTimer, QToolButton,
-    QVBoxLayout, QWidget, pyqtSignal, QDialogButtonBox, QSplitter
+    QAction, QApplication, QBrush, QCheckBox, QDialog, QDialogButtonBox, QGridLayout,
+    QHBoxLayout, QIcon, QKeySequence, QLabel, QListView, QModelIndex, QPalette, QPixmap,
+    QPushButton, QShortcut, QSize, QSplitter, Qt, QTimer, QToolButton, QVBoxLayout,
+    QWidget, pyqtSignal,
 )
 
 from calibre import fit_image
 from calibre.gui2 import NO_URL_FORMATTING, gprefs
 from calibre.gui2.book_details import (
-    create_open_cover_with_menu, css, details_context_menu_event, render_html,
-    set_html
+    create_open_cover_with_menu, css, details_context_menu_event, render_html, set_html,
 )
 from calibre.gui2.ui import get_gui
 from calibre.gui2.widgets import CoverView
 from calibre.gui2.widgets2 import Dialog, HTMLDisplay
+from calibre.startup import connect_lambda
 
 
 class Cover(CoverView):
@@ -60,7 +60,7 @@ class Configure(Dialog):
 
     def setup_ui(self):
         from calibre.gui2.preferences.look_feel import (
-            DisplayedFields, move_field_down, move_field_up
+            DisplayedFields, move_field_down, move_field_up,
         )
         self.l = QVBoxLayout(self)
         self.field_display_order = fdo = QListView(self)
diff --git a/src/calibre/gui2/dialogs/choose_format.py b/src/calibre/gui2/dialogs/choose_format.py
index f82946f79d..32b58034e7 100644
--- a/src/calibre/gui2/dialogs/choose_format.py
+++ b/src/calibre/gui2/dialogs/choose_format.py
@@ -2,12 +2,13 @@ __license__   = 'GPL v3'
 __copyright__ = '2008, Kovid Goyal <kovid at kovidgoyal.net>'
 
 from functools import partial
-
 from qt.core import (
-    QDialog, QListWidgetItem, QModelIndex, QIcon, QLabel, QVBoxLayout, QSize,
-    QDialogButtonBox, QListWidget, QHBoxLayout, QPushButton, QMenu)
+    QDialog, QDialogButtonBox, QHBoxLayout, QIcon, QLabel, QListWidget, QListWidgetItem,
+    QMenu, QModelIndex, QPushButton, QSize, QVBoxLayout,
+)
 
 from calibre.gui2 import file_icon_provider
+from calibre.startup import connect_lambda
 
 
 class ChooseFormatDialog(QDialog):
@@ -51,7 +52,7 @@ class ChooseFormatDialog(QDialog):
             self.update_open_with_button()
 
     def populate_open_with(self):
-        from calibre.gui2.open_with import populate_menu, edit_programs
+        from calibre.gui2.open_with import edit_programs, populate_menu
         menu = self.own
         menu.clear()
         fmt = self._formats[self.formats.currentRow()]
diff --git a/src/calibre/gui2/dialogs/confirm_delete.py b/src/calibre/gui2/dialogs/confirm_delete.py
index 24d7cf1498..1e161f1749 100644
--- a/src/calibre/gui2/dialogs/confirm_delete.py
+++ b/src/calibre/gui2/dialogs/confirm_delete.py
@@ -6,7 +6,7 @@ __copyright__ = '2008, Kovid Goyal kovid@kovidgoyal.net'
 __docformat__ = 'restructuredtext en'
 
 from qt.core import (
-    QDialog, Qt, QIcon, QVBoxLayout, QHBoxLayout, QLabel, QCheckBox, QDialogButtonBox
+    QCheckBox, QDialog, QDialogButtonBox, QHBoxLayout, QIcon, QLabel, Qt, QVBoxLayout,
 )
 
 from calibre import confirm_config_name
diff --git a/src/calibre/gui2/dialogs/confirm_delete_location.py b/src/calibre/gui2/dialogs/confirm_delete_location.py
index 98111edebb..3dacabbde0 100644
--- a/src/calibre/gui2/dialogs/confirm_delete_location.py
+++ b/src/calibre/gui2/dialogs/confirm_delete_location.py
@@ -6,8 +6,10 @@ __copyright__ = '2008, Kovid Goyal kovid@kovidgoyal.net' \
                 '2010, John Schember <john@nachtimwald.com>'
 __docformat__ = 'restructuredtext en'
 
+from qt.core import QDialog, QIcon, Qt
+
 from calibre.gui2.dialogs.confirm_delete_location_ui import Ui_Dialog
-from qt.core import QDialog, Qt, QIcon
+from calibre.startup import connect_lambda
 
 
 class Dialog(QDialog, Ui_Dialog):
diff --git a/src/calibre/gui2/dialogs/confirm_merge.py b/src/calibre/gui2/dialogs/confirm_merge.py
index 7e6dfe71d7..268b9b21ca 100644
--- a/src/calibre/gui2/dialogs/confirm_merge.py
+++ b/src/calibre/gui2/dialogs/confirm_merge.py
@@ -5,14 +5,16 @@ __license__ = 'GPL v3'
 __copyright__ = '2015, Kovid Goyal <kovid at kovidgoyal.net>'
 
 from qt.core import (
-    QVBoxLayout, QSplitter, QWidget, QLabel, QCheckBox, QTextBrowser, Qt, QDialog, QDialogButtonBox
+    QCheckBox, QDialog, QDialogButtonBox, QLabel, QSplitter, Qt, QTextBrowser,
+    QVBoxLayout, QWidget,
 )
 
 from calibre.ebooks.metadata import authors_to_string
 from calibre.ebooks.metadata.book.base import field_metadata
 from calibre.gui2 import dynamic, gprefs
-from calibre.gui2.widgets2 import Dialog
 from calibre.gui2.dialogs.confirm_delete import confirm_config_name
+from calibre.gui2.widgets2 import Dialog
+from calibre.startup import connect_lambda
 from calibre.utils.config import tweaks
 from calibre.utils.date import format_date
 
diff --git a/src/calibre/gui2/dialogs/exim.py b/src/calibre/gui2/dialogs/exim.py
index 2d33a181fd..f0c9701ee3 100644
--- a/src/calibre/gui2/dialogs/exim.py
+++ b/src/calibre/gui2/dialogs/exim.py
@@ -2,22 +2,23 @@
 # License: GPLv3 Copyright: 2015, Kovid Goyal <kovid at kovidgoyal.net>
 
 
+import os
+import stat
 from functools import partial
-from threading import Thread, Event
-import os, stat
-
 from qt.core import (
-    QSize, QStackedLayout, QWidget, QVBoxLayout, QLabel, QPushButton,
-    QListWidget, QListWidgetItem, QIcon, Qt, pyqtSignal, QGridLayout,
-    QProgressBar, QDialog, QDialogButtonBox, QScrollArea, QLineEdit, QFrame, QAbstractItemView
+    QAbstractItemView, QDialog, QDialogButtonBox, QFrame, QGridLayout, QIcon, QLabel,
+    QLineEdit, QListWidget, QListWidgetItem, QProgressBar, QPushButton, QScrollArea,
+    QSize, QStackedLayout, Qt, QVBoxLayout, QWidget, pyqtSignal,
 )
+from threading import Event, Thread
 
-from calibre import human_readable, as_unicode
+from calibre import as_unicode, human_readable
 from calibre.constants import iswindows
 from calibre.db.legacy import LibraryDatabase
 from calibre.gui2 import choose_dir, error_dialog, question_dialog
 from calibre.gui2.widgets2 import Dialog
-from calibre.utils.exim import all_known_libraries, export, Importer, import_data
+from calibre.startup import connect_lambda
+from calibre.utils.exim import Importer, all_known_libraries, export, import_data
 from calibre.utils.icu import numeric_sort_key
 
 
diff --git a/src/calibre/gui2/dialogs/metadata_bulk.py b/src/calibre/gui2/dialogs/metadata_bulk.py
index a5c975db55..ee84c037e9 100644
--- a/src/calibre/gui2/dialogs/metadata_bulk.py
+++ b/src/calibre/gui2/dialogs/metadata_bulk.py
@@ -28,6 +28,7 @@ from calibre.gui2.dialogs.metadata_bulk_ui import Ui_MetadataBulkDialog
 from calibre.gui2.dialogs.tag_editor import TagEditor
 from calibre.gui2.dialogs.template_line_editor import TemplateLineEditor
 from calibre.gui2.widgets import LineEditECM
+from calibre.startup import connect_lambda
 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 (
diff --git a/src/calibre/gui2/dialogs/search.py b/src/calibre/gui2/dialogs/search.py
index c3589c8da8..876ceffbf8 100644
--- a/src/calibre/gui2/dialogs/search.py
+++ b/src/calibre/gui2/dialogs/search.py
@@ -1,22 +1,23 @@
 __license__   = 'GPL v3'
 __copyright__ = '2008, Kovid Goyal <kovid at kovidgoyal.net>'
 
-import re, copy
+import copy
+import re
 from datetime import date
-
 from qt.core import (
-    QDialog, QDialogButtonBox, QFrame, QLabel, QComboBox, QIcon, QVBoxLayout, Qt,
-    QSize, QHBoxLayout, QTabWidget, QLineEdit, QWidget, QGroupBox, QFormLayout,
-    QSpinBox, QRadioButton, QPushButton, QToolButton
+    QComboBox, QDialog, QDialogButtonBox, QFormLayout, QFrame, QGroupBox, QHBoxLayout,
+    QIcon, QLabel, QLineEdit, QPushButton, QRadioButton, QSize, QSpinBox, Qt,
+    QTabWidget, QToolButton, QVBoxLayout, QWidget,
 )
 
 from calibre import strftime
-from calibre.library.caches import CONTAINS_MATCH, EQUALS_MATCH, REGEXP_MATCH
 from calibre.gui2 import gprefs
 from calibre.gui2.complete2 import EditWithComplete
-from calibre.utils.icu import sort_key
+from calibre.library.caches import CONTAINS_MATCH, EQUALS_MATCH, REGEXP_MATCH
+from calibre.startup import connect_lambda
 from calibre.utils.config import tweaks
 from calibre.utils.date import now
+from calibre.utils.icu import sort_key
 from calibre.utils.localization import localize_user_manual_link
 
 box_values = {}
diff --git a/src/calibre/gui2/dialogs/tag_editor.py b/src/calibre/gui2/dialogs/tag_editor.py
index 5c0bd60df0..1a979546ed 100644
--- a/src/calibre/gui2/dialogs/tag_editor.py
+++ b/src/calibre/gui2/dialogs/tag_editor.py
@@ -9,6 +9,7 @@ from calibre.constants import islinux
 from calibre.gui2 import error_dialog, gprefs, question_dialog
 from calibre.gui2.dialogs.confirm_delete import confirm
 from calibre.gui2.dialogs.tag_editor_ui import Ui_TagEditor
+from calibre.startup import connect_lambda
 from calibre.utils.icu import sort_key
 
 
diff --git a/src/calibre/gui2/gestures.py b/src/calibre/gui2/gestures.py
index 8688dae217..1b60d1951c 100644
--- a/src/calibre/gui2/gestures.py
+++ b/src/calibre/gui2/gestures.py
@@ -6,9 +6,10 @@ import os
 from functools import lru_cache
 from qt.core import (
     QApplication, QEvent, QInputDevice, QMouseEvent, QObject, QPointF, QScroller, Qt,
-    pyqtSignal
+    pyqtSignal,
 )
 
+from calibre.startup import connect_lambda
 from calibre.utils.monotonic import monotonic
 from polyglot.builtins import itervalues
 
diff --git a/src/calibre/gui2/jobs.py b/src/calibre/gui2/jobs.py
index 700f24475c..6b1368e94e 100644
--- a/src/calibre/gui2/jobs.py
+++ b/src/calibre/gui2/jobs.py
@@ -27,6 +27,7 @@ from calibre.gui2.dialogs.jobs_ui import Ui_JobsDialog
 from calibre.gui2.progress_indicator import ProgressIndicator
 from calibre.gui2.threaded_jobs import ThreadedJob, ThreadedJobServer
 from calibre.gui2.widgets2 import Dialog
+from calibre.startup import connect_lambda
 from calibre.utils.icu import lower
 from calibre.utils.ipc.job import ParallelJob
 from calibre.utils.ipc.server import Server
diff --git a/src/calibre/gui2/library/annotations.py b/src/calibre/gui2/library/annotations.py
index 60c36ab53d..ad0038553d 100644
--- a/src/calibre/gui2/library/annotations.py
+++ b/src/calibre/gui2/library/annotations.py
@@ -29,6 +29,7 @@ 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.startup import connect_lambda
 from calibre.utils.localization import ngettext
 
 
diff --git a/src/calibre/gui2/metadata/bulk_download.py b/src/calibre/gui2/metadata/bulk_download.py
index 03cbeed404..b744635ce9 100644
--- a/src/calibre/gui2/metadata/bulk_download.py
+++ b/src/calibre/gui2/metadata/bulk_download.py
@@ -14,6 +14,7 @@ from threading import Thread
 from calibre.ebooks.metadata.opf2 import metadata_to_opf
 from calibre.gui2.threaded_jobs import ThreadedJob
 from calibre.ptempfile import PersistentTemporaryDirectory, PersistentTemporaryFile
+from calibre.startup import connect_lambda
 from calibre.utils.ipc.simple_worker import WorkerError, fork_job
 from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems
diff --git a/src/calibre/gui2/metadata/diff.py b/src/calibre/gui2/metadata/diff.py
index 4266ba1239..5140fcb6b6 100644
--- a/src/calibre/gui2/metadata/diff.py
+++ b/src/calibre/gui2/metadata/diff.py
@@ -25,6 +25,7 @@ from calibre.gui2.languages import LanguagesEdit as LE
 from calibre.gui2.metadata.basic_widgets import PubdateEdit, RatingEdit
 from calibre.gui2.widgets2 import RightClickButton
 from calibre.ptempfile import PersistentTemporaryFile
+from calibre.startup import connect_lambda
 from calibre.utils.date import UNDEFINED_DATE
 from calibre.utils.icu import lower as icu_lower
 from calibre.utils.localization import ngettext
diff --git a/src/calibre/gui2/preferences/emailp.py b/src/calibre/gui2/preferences/emailp.py
index bc5731d5c8..3b4c34b0a7 100644
--- a/src/calibre/gui2/preferences/emailp.py
+++ b/src/calibre/gui2/preferences/emailp.py
@@ -4,12 +4,12 @@
 
 import re
 import textwrap
-
-from qt.core import QAbstractTableModel, QFont, Qt, QAbstractItemView
+from qt.core import QAbstractItemView, QAbstractTableModel, QFont, Qt
 
 from calibre.gui2 import gprefs
 from calibre.gui2.preferences import AbortCommit, ConfigWidgetBase, test_widget
 from calibre.gui2.preferences.email_ui import Ui_Form
+from calibre.startup import connect_lambda
 from calibre.utils.config import ConfigProxy
 from calibre.utils.icu import numeric_sort_key
 from calibre.utils.smtp import config as smtp_prefs
diff --git a/src/calibre/gui2/preferences/look_feel.py b/src/calibre/gui2/preferences/look_feel.py
index ae951cc5e8..80099d1134 100644
--- a/src/calibre/gui2/preferences/look_feel.py
+++ b/src/calibre/gui2/preferences/look_feel.py
@@ -37,6 +37,7 @@ from calibre.gui2.preferences.coloring import EditRules
 from calibre.gui2.preferences.look_feel_ui import Ui_Form
 from calibre.gui2.widgets import BusyCursor
 from calibre.gui2.widgets2 import Dialog
+from calibre.startup import connect_lambda
 from calibre.utils.config import prefs
 from calibre.utils.icu import sort_key
 from calibre.utils.localization import available_translations, get_lang, get_language
diff --git a/src/calibre/gui2/preferences/toolbar.py b/src/calibre/gui2/preferences/toolbar.py
index aaeab85101..44c6945e3d 100644
--- a/src/calibre/gui2/preferences/toolbar.py
+++ b/src/calibre/gui2/preferences/toolbar.py
@@ -5,12 +5,13 @@ __license__   = 'GPL v3'
 __copyright__ = '2010, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-from qt.core import QAbstractListModel, Qt, QIcon, QItemSelectionModel
+from qt.core import QAbstractListModel, QIcon, QItemSelectionModel, Qt
 
 from calibre import force_unicode
+from calibre.gui2 import error_dialog, gprefs, warning_dialog
+from calibre.gui2.preferences import AbortCommit, ConfigWidgetBase, test_widget
 from calibre.gui2.preferences.toolbar_ui import Ui_Form
-from calibre.gui2 import gprefs, warning_dialog, error_dialog
-from calibre.gui2.preferences import ConfigWidgetBase, test_widget, AbortCommit
+from calibre.startup import connect_lambda
 from calibre.utils.icu import primary_sort_key
 
 
diff --git a/src/calibre/gui2/store/web_store.py b/src/calibre/gui2/store/web_store.py
index 6895b5f031..4647d40b47 100644
--- a/src/calibre/gui2/store/web_store.py
+++ b/src/calibre/gui2/store/web_store.py
@@ -7,22 +7,23 @@ import os
 import shutil
 from qt.core import (
     QApplication, QHBoxLayout, QIcon, QLabel, QProgressBar, QPushButton, QSize, QUrl,
-    QVBoxLayout, QWidget, pyqtSignal
+    QVBoxLayout, QWidget, pyqtSignal,
 )
 from qt.webengine import (
-    QWebEngineDownloadRequest, QWebEnginePage, QWebEngineProfile, QWebEngineView
+    QWebEngineDownloadRequest, QWebEnginePage, QWebEngineProfile, QWebEngineView,
 )
 
 from calibre import random_user_agent, url_slash_cleaner
 from calibre.constants import STORE_DIALOG_APP_UID, islinux, iswindows
 from calibre.ebooks import BOOK_EXTENSIONS
 from calibre.gui2 import (
-    Application, choose_save_file, error_dialog, gprefs, info_dialog, set_app_uid
+    Application, choose_save_file, error_dialog, gprefs, info_dialog, set_app_uid,
 )
 from calibre.gui2.dialogs.confirm_delete import confirm
 from calibre.gui2.listener import send_message_in_process
 from calibre.gui2.main_window import MainWindow
 from calibre.ptempfile import PersistentTemporaryDirectory, reset_base_dir
+from calibre.startup import connect_lambda
 from calibre.utils.webengine import setup_profile
 from polyglot.binary import as_base64_bytes, from_base64_bytes
 from polyglot.builtins import string_or_bytes
diff --git a/src/calibre/gui2/tag_browser/ui.py b/src/calibre/gui2/tag_browser/ui.py
index d4c67d2997..34afb2951d 100644
--- a/src/calibre/gui2/tag_browser/ui.py
+++ b/src/calibre/gui2/tag_browser/ui.py
@@ -22,6 +22,7 @@ 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.startup import connect_lambda
 from calibre.utils.icu import sort_key
 from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems
diff --git a/src/calibre/gui2/tag_mapper.py b/src/calibre/gui2/tag_mapper.py
index 0f11a3fd03..d3e990b2e1 100644
--- a/src/calibre/gui2/tag_mapper.py
+++ b/src/calibre/gui2/tag_mapper.py
@@ -16,6 +16,7 @@ from calibre.gui2 import Application, error_dialog, question_dialog
 from calibre.gui2.complete2 import EditWithComplete
 from calibre.gui2.ui import get_gui
 from calibre.gui2.widgets2 import Dialog
+from calibre.startup import connect_lambda
 from calibre.utils.config import JSONConfig
 from calibre.utils.localization import localize_user_manual_link
 from polyglot.builtins import iteritems
diff --git a/src/calibre/gui2/toc/main.py b/src/calibre/gui2/toc/main.py
index 50f1e6565b..fcb293c22c 100644
--- a/src/calibre/gui2/toc/main.py
+++ b/src/calibre/gui2/toc/main.py
@@ -26,6 +26,7 @@ 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.startup import connect_lambda
 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
diff --git a/src/calibre/gui2/tweak_book/boss.py b/src/calibre/gui2/tweak_book/boss.py
index 7958bef8eb..3b397203e4 100644
--- a/src/calibre/gui2/tweak_book/boss.py
+++ b/src/calibre/gui2/tweak_book/boss.py
@@ -61,6 +61,7 @@ from calibre.gui2.tweak_book.widgets import (
 )
 from calibre.gui2.widgets import BusyCursor
 from calibre.ptempfile import PersistentTemporaryDirectory, TemporaryDirectory
+from calibre.startup import connect_lambda
 from calibre.utils.config import JSONConfig
 from calibre.utils.icu import numeric_sort_key
 from calibre.utils.imghdr import identify
diff --git a/src/calibre/gui2/tweak_book/char_select.py b/src/calibre/gui2/tweak_book/char_select.py
index 59cc8d6be7..d58ef2e8df 100644
--- a/src/calibre/gui2/tweak_book/char_select.py
+++ b/src/calibre/gui2/tweak_book/char_select.py
@@ -9,16 +9,17 @@ import textwrap
 from bisect import bisect
 from functools import partial
 from qt.core import (
-    QAbstractItemModel, QAbstractListModel, QApplication, QCheckBox, QGridLayout,
-    QHBoxLayout, QIcon, QInputMethodEvent, QLabel, QListView, QMenu, QMimeData,
-    QModelIndex, QPen, QPushButton, QSize, QSizePolicy, QSplitter,
-    QStyledItemDelegate, Qt, QToolButton, QTreeView, pyqtSignal, QAbstractItemView, QDialogButtonBox
+    QAbstractItemModel, QAbstractItemView, QAbstractListModel, QApplication, QCheckBox,
+    QDialogButtonBox, QGridLayout, QHBoxLayout, QIcon, QInputMethodEvent, QLabel,
+    QListView, QMenu, QMimeData, QModelIndex, QPen, QPushButton, QSize, QSizePolicy,
+    QSplitter, QStyledItemDelegate, Qt, QToolButton, QTreeView, pyqtSignal,
 )
 
 from calibre.gui2.tweak_book import tprefs
 from calibre.gui2.tweak_book.widgets import Dialog
 from calibre.gui2.widgets import BusyCursor
 from calibre.gui2.widgets2 import HistoryLineEdit2
+from calibre.startup import connect_lambda
 from calibre.utils.icu import safe_chr as codepoint_to_chr
 from calibre.utils.unicode_names import character_name_from_code, points_for_word
 from calibre_extensions.progress_indicator import set_no_activate_on_click
diff --git a/src/calibre/gui2/tweak_book/diff/main.py b/src/calibre/gui2/tweak_book/diff/main.py
index 04e8340fac..9ae3ded1d1 100644
--- a/src/calibre/gui2/tweak_book/diff/main.py
+++ b/src/calibre/gui2/tweak_book/diff/main.py
@@ -4,22 +4,26 @@
 __license__ = 'GPL v3'
 __copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'
 
-import sys, os, re, textwrap
+import os
+import re
+import sys
+import textwrap
 from functools import partial
-
 from qt.core import (
-    QGridLayout, QToolButton, QIcon, QRadioButton, QMenu, QApplication, Qt,
-    QSize, QWidget, QLabel, QStackedLayout, QPainter, QRect, QVBoxLayout,
-    QCursor, QEventLoop, QKeySequence, pyqtSignal, QTimer, QHBoxLayout, QDialogButtonBox)
+    QApplication, QCursor, QDialogButtonBox, QEventLoop, QGridLayout, QHBoxLayout,
+    QIcon, QKeySequence, QLabel, QMenu, QPainter, QRadioButton, QRect, QSize,
+    QStackedLayout, Qt, QTimer, QToolButton, QVBoxLayout, QWidget, pyqtSignal,
+)
 
 from calibre.ebooks.oeb.polish.container import Container
 from calibre.ebooks.oeb.polish.utils import guess_type
 from calibre.gui2 import info_dialog
 from calibre.gui2.progress_indicator import ProgressIndicator
-from calibre.gui2.tweak_book.editor import syntax_from_mime
 from calibre.gui2.tweak_book.diff.view import DiffView
+from calibre.gui2.tweak_book.editor import syntax_from_mime
 from calibre.gui2.tweak_book.widgets import Dialog
 from calibre.gui2.widgets2 import HistoryLineEdit2
+from calibre.startup import connect_lambda
 from calibre.utils.filenames import samefile
 from calibre.utils.icu import numeric_sort_key
 from polyglot.builtins import iteritems
@@ -97,7 +101,7 @@ def changed_files(list_of_names1, list_of_names2, get_data1, get_data2):
 
 
 def get_decoded_raw(name):
-    from calibre.ebooks.chardet import xml_to_unicode, force_encoding
+    from calibre.ebooks.chardet import force_encoding, xml_to_unicode
     with open(name, 'rb') as f:
         raw = f.read()
     syntax = syntax_from_mime(name, guess_type(name))
diff --git a/src/calibre/gui2/tweak_book/diff/view.py b/src/calibre/gui2/tweak_book/diff/view.py
index 39ee3fc07c..3b023420ed 100644
--- a/src/calibre/gui2/tweak_book/diff/view.py
+++ b/src/calibre/gui2/tweak_book/diff/view.py
@@ -10,10 +10,10 @@ from functools import partial
 from itertools import chain
 from math import ceil
 from qt.core import (
-    QApplication, QBrush, QColor, QEvent, QEventLoop, QFont, QHBoxLayout,
-    QIcon, QImage, QKeySequence, QMenu, QPainter, QPainterPath, QPalette, QPen,
-    QPixmap, QPlainTextEdit, QRect, QScrollBar, QSplitter, QSplitterHandle, Qt,
-    QTextCharFormat, QTextCursor, QTextLayout, QTimer, QWidget, pyqtSignal
+    QApplication, QBrush, QColor, QEvent, QEventLoop, QFont, QHBoxLayout, QIcon, QImage,
+    QKeySequence, QMenu, QPainter, QPainterPath, QPalette, QPen, QPixmap,
+    QPlainTextEdit, QRect, QScrollBar, QSplitter, QSplitterHandle, Qt, QTextCharFormat,
+    QTextCursor, QTextLayout, QTimer, QWidget, pyqtSignal,
 )
 
 from calibre import fit_image, human_readable
@@ -22,10 +22,11 @@ from calibre.gui2.tweak_book import tprefs
 from calibre.gui2.tweak_book.diff import get_sequence_matcher
 from calibre.gui2.tweak_book.diff.highlight import get_highlighter
 from calibre.gui2.tweak_book.editor.text import (
-    LineNumbers, PlainTextEdit, default_font_family
+    LineNumbers, PlainTextEdit, default_font_family,
 )
 from calibre.gui2.tweak_book.editor.themes import get_theme, theme_color
 from calibre.gui2.widgets import BusyCursor
+from calibre.startup import connect_lambda
 from calibre.utils.icu import utf16_length
 from calibre.utils.xml_parse import safe_xml_fromstring
 from polyglot.builtins import as_bytes, iteritems
diff --git a/src/calibre/gui2/tweak_book/download.py b/src/calibre/gui2/tweak_book/download.py
index 246c5b46c1..97b09b84df 100644
--- a/src/calibre/gui2/tweak_book/download.py
+++ b/src/calibre/gui2/tweak_book/download.py
@@ -15,6 +15,7 @@ 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.startup import connect_lambda
 from calibre.utils.localization import ngettext
 from polyglot.builtins import iteritems
 
diff --git a/src/calibre/gui2/tweak_book/editor/image.py b/src/calibre/gui2/tweak_book/editor/image.py
index 277433123f..715ac47963 100644
--- a/src/calibre/gui2/tweak_book/editor/image.py
+++ b/src/calibre/gui2/tweak_book/editor/image.py
@@ -5,14 +5,16 @@ __license__ = 'GPL v3'
 __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
 import sys
-
 from qt.core import (
-    QMainWindow, Qt, QApplication, pyqtSignal, QLabel, QIcon, QFormLayout, QSize,
-    QDialog, QSpinBox, QCheckBox, QDialogButtonBox, QToolButton, QMenu, QInputDialog)
+    QApplication, QCheckBox, QDialog, QDialogButtonBox, QFormLayout, QIcon,
+    QInputDialog, QLabel, QMainWindow, QMenu, QSize, QSpinBox, Qt, QToolButton,
+    pyqtSignal,
+)
 
 from calibre.gui2 import error_dialog
-from calibre.gui2.tweak_book import actions, tprefs, editors
+from calibre.gui2.tweak_book import actions, editors, tprefs
 from calibre.gui2.tweak_book.editor.canvas import Canvas
+from calibre.startup import connect_lambda
 from polyglot.builtins import itervalues
 
 
diff --git a/src/calibre/gui2/tweak_book/editor/insert_resource.py b/src/calibre/gui2/tweak_book/editor/insert_resource.py
index d7ec9bde5c..d4ced61597 100644
--- a/src/calibre/gui2/tweak_book/editor/insert_resource.py
+++ b/src/calibre/gui2/tweak_book/editor/insert_resource.py
@@ -8,10 +8,11 @@ import os
 import sys
 from functools import partial
 from qt.core import (
-    QAbstractListModel, QApplication, QCheckBox, QFormLayout, QGridLayout, QClipboard,
-    QHBoxLayout, QIcon, QInputDialog, QLabel, QLineEdit, QListView, QMenu, QPainter,
-    QPixmap, QRect, QSize, QSizePolicy, QSortFilterProxyModel, QStyledItemDelegate,
-    Qt, QToolButton, QTreeWidget, QTreeWidgetItem, QVBoxLayout, pyqtSignal, QDialog, QDialogButtonBox
+    QAbstractListModel, QApplication, QCheckBox, QClipboard, QDialog, QDialogButtonBox,
+    QFormLayout, QGridLayout, QHBoxLayout, QIcon, QInputDialog, QLabel, QLineEdit,
+    QListView, QMenu, QPainter, QPixmap, QRect, QSize, QSizePolicy,
+    QSortFilterProxyModel, QStyledItemDelegate, Qt, QToolButton, QTreeWidget,
+    QTreeWidgetItem, QVBoxLayout, pyqtSignal,
 )
 
 from calibre import fit_image
@@ -23,6 +24,7 @@ from calibre.gui2.tweak_book import current_container, tprefs
 from calibre.gui2.tweak_book.file_list import name_is_ok
 from calibre.gui2.tweak_book.widgets import Dialog
 from calibre.ptempfile import PersistentTemporaryFile
+from calibre.startup import connect_lambda
 from calibre.utils.icu import numeric_sort_key
 from calibre.utils.localization import canonicalize_lang, get_lang
 from calibre_extensions.progress_indicator import set_no_activate_on_click
diff --git a/src/calibre/gui2/tweak_book/file_list.py b/src/calibre/gui2/tweak_book/file_list.py
index 1eb9dfef9f..056fc6df6c 100644
--- a/src/calibre/gui2/tweak_book/file_list.py
+++ b/src/calibre/gui2/tweak_book/file_list.py
@@ -35,6 +35,7 @@ from calibre.gui2.tweak_book import (
 )
 from calibre.gui2.tweak_book.editor import syntax_from_mime
 from calibre.gui2.tweak_book.templates import template_for
+from calibre.startup import connect_lambda
 from calibre.utils.fonts.utils import get_font_names
 from calibre.utils.icu import numeric_sort_key
 from calibre.utils.localization import ngettext, pgettext
diff --git a/src/calibre/gui2/tweak_book/polish.py b/src/calibre/gui2/tweak_book/polish.py
index 80b23ea99e..4ddfa0b2f2 100644
--- a/src/calibre/gui2/tweak_book/polish.py
+++ b/src/calibre/gui2/tweak_book/polish.py
@@ -5,20 +5,20 @@ __license__ = 'GPL v3'
 __copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'
 
 import re
+from qt.core import (
+    QAbstractItemView, QApplication, QCheckBox, QDialog, QDialogButtonBox, QHBoxLayout,
+    QIcon, QLabel, QListWidget, QListWidgetItem, QPalette, QPen, QPixmap, QProgressBar,
+    QSize, QSpinBox, QStyle, QStyledItemDelegate, Qt, QTextBrowser, QVBoxLayout,
+    pyqtSignal,
+)
 from threading import Thread
 
-from qt.core import (
-    QTextBrowser, QVBoxLayout, QDialog, QDialogButtonBox, QIcon, QLabel,
-    QCheckBox, Qt, QListWidgetItem, QHBoxLayout, QListWidget, QPixmap,
-    QSpinBox, QStyledItemDelegate, QSize, QStyle, QPen, QPalette,
-    QProgressBar, pyqtSignal, QApplication, QAbstractItemView
-)
-
-from calibre import human_readable, fit_image, force_unicode
+from calibre import fit_image, force_unicode, human_readable
 from calibre.ebooks.oeb.polish.main import CUSTOMIZATION
 from calibre.gui2 import empty_index, question_dialog
-from calibre.gui2.tweak_book import tprefs, current_container, set_current_container
+from calibre.gui2.tweak_book import current_container, set_current_container, tprefs
 from calibre.gui2.tweak_book.widgets import Dialog
+from calibre.startup import connect_lambda
 from calibre.utils.icu import numeric_sort_key
 
 
@@ -254,8 +254,8 @@ class CompressImagesProgress(Dialog):
         t.start()
 
     def run_compress(self):
-        from calibre.gui2.tweak_book import current_container
         from calibre.ebooks.oeb.polish.images import compress_images
+        from calibre.gui2.tweak_book import current_container
         report = []
         try:
             self.result = (compress_images(
@@ -304,7 +304,9 @@ class CompressImagesProgress(Dialog):
 if __name__ == '__main__':
     from calibre.gui2 import Application
     app = Application([])
-    import sys, sip
+    import sip
+    import sys
+
     from calibre.ebooks.oeb.polish.container import get_container
     c = get_container(sys.argv[-1], tweak_mode=True)
     set_current_container(c)
diff --git a/src/calibre/gui2/tweak_book/preferences.py b/src/calibre/gui2/tweak_book/preferences.py
index 506d316538..942fdc6f76 100644
--- a/src/calibre/gui2/tweak_book/preferences.py
+++ b/src/calibre/gui2/tweak_book/preferences.py
@@ -31,6 +31,7 @@ from calibre.gui2.tweak_book.editor.themes import (
 from calibre.gui2.tweak_book.spell import ManageDictionaries
 from calibre.gui2.tweak_book.widgets import Dialog
 from calibre.gui2.widgets2 import ColorButton
+from calibre.startup import connect_lambda
 from calibre.utils.localization import get_lang, ngettext
 from polyglot.builtins import iteritems, itervalues
 
diff --git a/src/calibre/gui2/tweak_book/search.py b/src/calibre/gui2/tweak_book/search.py
index d864bcd06f..80fd278c40 100644
--- a/src/calibre/gui2/tweak_book/search.py
+++ b/src/calibre/gui2/tweak_book/search.py
@@ -1,7 +1,6 @@
 #!/usr/bin/env python
 # License: GPLv3 Copyright: 2013, Kovid Goyal <kovid at kovidgoyal.net>
 
-
 import copy
 import json
 import regex
@@ -9,32 +8,33 @@ import time
 from collections import Counter, OrderedDict
 from functools import partial
 from qt.core import (
-    QAbstractListModel, QAction, QApplication, QCheckBox, QComboBox, QFont, QFrame,
-    QGridLayout, QHBoxLayout, QIcon, QItemSelection, QKeySequence, QLabel, QLineEdit,
-    QListView, QMenu, QMimeData, QModelIndex, QPushButton, QScrollArea, QSize, QItemSelectionModel,
-    QSizePolicy, QStackedLayout, QStyledItemDelegate, Qt, QTimer, QToolBar, QDialog,
-    QToolButton, QVBoxLayout, QWidget, pyqtSignal, QAbstractItemView, QEvent, QDialogButtonBox
+    QAbstractItemView, QAbstractListModel, QAction, QApplication, QCheckBox, QComboBox,
+    QDialog, QDialogButtonBox, QEvent, QFont, QFrame, QGridLayout, QHBoxLayout, QIcon,
+    QItemSelection, QItemSelectionModel, QKeySequence, QLabel, QLineEdit, QListView,
+    QMenu, QMimeData, QModelIndex, QPushButton, QScrollArea, QSize, QSizePolicy,
+    QStackedLayout, QStyledItemDelegate, Qt, QTimer, QToolBar, QToolButton, QVBoxLayout,
+    QWidget, pyqtSignal,
 )
 
 from calibre import prepare_string_for_xml
 from calibre.constants import iswindows
 from calibre.ebooks.conversion.search_replace import (
-    REGEX_FLAGS, compile_regular_expression
+    REGEX_FLAGS, compile_regular_expression,
 )
 from calibre.gui2 import choose_files, choose_save_file, error_dialog, info_dialog
 from calibre.gui2.dialogs.confirm_delete import confirm
 from calibre.gui2.dialogs.message_box import MessageBox
 from calibre.gui2.tweak_book import current_container, editors, tprefs
 from calibre.gui2.tweak_book.editor.snippets import (
-    KEY, MODIFIER, SnippetTextEdit, find_matching_snip, parse_template,
-    string_length
+    KEY, MODIFIER, SnippetTextEdit, find_matching_snip, parse_template, string_length,
 )
 from calibre.gui2.tweak_book.function_replace import (
     Function, FunctionBox, FunctionEditor, functions as replace_functions,
-    remove_function
+    remove_function,
 )
 from calibre.gui2.widgets import BusyCursor
 from calibre.gui2.widgets2 import FlowLayout, HistoryComboBox
+from calibre.startup import connect_lambda
 from calibre.utils.icu import primary_contains
 from polyglot.builtins import error_message, iteritems
 
diff --git a/src/calibre/gui2/tweak_book/spell.py b/src/calibre/gui2/tweak_book/spell.py
index 3ab38c25bf..34f7bfaca7 100644
--- a/src/calibre/gui2/tweak_book/spell.py
+++ b/src/calibre/gui2/tweak_book/spell.py
@@ -41,6 +41,7 @@ from calibre.spell.dictionary import (
     get_dictionary, remove_dictionary, rename_dictionary,
 )
 from calibre.spell.import_from import import_from_oxt
+from calibre.startup import connect_lambda
 from calibre.utils.icu import contains, primary_contains, primary_sort_key, sort_key
 from calibre.utils.localization import (
     calibre_langcode_to_name, canonicalize_lang, get_lang, get_language,
diff --git a/src/calibre/gui2/tweak_book/text_search.py b/src/calibre/gui2/tweak_book/text_search.py
index 5f28212c4e..d67c712dc8 100644
--- a/src/calibre/gui2/tweak_book/text_search.py
+++ b/src/calibre/gui2/tweak_book/text_search.py
@@ -2,19 +2,22 @@
 # License: GPLv3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>
 
 
-from qt.core import (
-    QWidget, QHBoxLayout, QVBoxLayout, QLabel, QComboBox, QPushButton, QIcon,
-    pyqtSignal, QFont, QCheckBox, QSizePolicy
-)
 from lxml.etree import tostring
+from qt.core import (
+    QCheckBox, QComboBox, QFont, QHBoxLayout, QIcon, QLabel, QPushButton, QSizePolicy,
+    QVBoxLayout, QWidget, pyqtSignal,
+)
 
 from calibre import prepare_string_for_xml
 from calibre.gui2 import error_dialog
-from calibre.gui2.tweak_book import tprefs, editors, current_container
-from calibre.gui2.tweak_book.search import get_search_regex, InvalidRegex, initialize_search_request
+from calibre.gui2.tweak_book import current_container, editors, tprefs
+from calibre.gui2.tweak_book.search import (
+    InvalidRegex, get_search_regex, initialize_search_request,
+)
 from calibre.gui2.widgets import BusyCursor
 from calibre.gui2.widgets2 import HistoryComboBox
-from polyglot.builtins import iteritems, error_message
+from calibre.startup import connect_lambda
+from polyglot.builtins import error_message, iteritems
 
 # UI {{{
 
diff --git a/src/calibre/gui2/tweak_book/widgets.py b/src/calibre/gui2/tweak_book/widgets.py
index bc9e2bb889..1b492ae80f 100644
--- a/src/calibre/gui2/tweak_book/widgets.py
+++ b/src/calibre/gui2/tweak_book/widgets.py
@@ -10,35 +10,36 @@ import unicodedata
 from collections import OrderedDict
 from math import ceil
 from qt.core import (
-    QAbstractListModel, QApplication, QCheckBox, QComboBox, QDialog,
-    QDialogButtonBox, QEvent, QFormLayout, QFrame, QGridLayout, QGroupBox,
-    QHBoxLayout, QIcon, QItemSelectionModel, QLabel, QLineEdit, QListView, QMimeData,
-    QModelIndex, QPainter, QPalette, QPixmap, QPlainTextEdit, QPoint, QRect, QSize,
-    QSizePolicy, QSplitter, QStaticText, QStyle, QStyledItemDelegate, Qt, QTextCursor,
-    QTextDocument, QTextOption, QToolButton, QVBoxLayout, QWidget, pyqtSignal
+    QAbstractListModel, QApplication, QCheckBox, QComboBox, QDialog, QDialogButtonBox,
+    QEvent, QFormLayout, QFrame, QGridLayout, QGroupBox, QHBoxLayout, QIcon,
+    QItemSelectionModel, QLabel, QLineEdit, QListView, QMimeData, QModelIndex, QPainter,
+    QPalette, QPixmap, QPlainTextEdit, QPoint, QRect, QSize, QSizePolicy, QSplitter,
+    QStaticText, QStyle, QStyledItemDelegate, Qt, QTextCursor, QTextDocument,
+    QTextOption, QToolButton, QVBoxLayout, QWidget, pyqtSignal,
 )
 
 from calibre import human_readable, prepare_string_for_xml
 from calibre.constants import iswindows
 from calibre.ebooks.oeb.polish.cover import get_raster_cover_name
 from calibre.ebooks.oeb.polish.toc import (
-    ensure_container_has_nav, get_guide_landmarks, get_nav_landmarks, set_landmarks
+    ensure_container_has_nav, get_guide_landmarks, get_nav_landmarks, set_landmarks,
 )
 from calibre.ebooks.oeb.polish.upgrade import guide_epubtype_map
 from calibre.ebooks.oeb.polish.utils import guess_type, lead_text
 from calibre.gui2 import (
-    choose_files, choose_images, choose_save_file, error_dialog, info_dialog
+    choose_files, choose_images, choose_save_file, error_dialog, info_dialog,
 )
 from calibre.gui2.complete2 import EditWithComplete
 from calibre.gui2.tweak_book import current_container, tprefs
 from calibre.gui2.widgets2 import (
-    PARAGRAPH_SEPARATOR, Dialog as BaseDialog, HistoryComboBox, to_plain_text
+    PARAGRAPH_SEPARATOR, Dialog as BaseDialog, HistoryComboBox, to_plain_text,
 )
+from calibre.startup import connect_lambda
 from calibre.utils.icu import (
-    numeric_sort_key, primary_contains, primary_sort_key, sort_key
+    numeric_sort_key, primary_contains, primary_sort_key, sort_key,
 )
 from calibre.utils.matcher import (
-    DEFAULT_LEVEL1, DEFAULT_LEVEL2, DEFAULT_LEVEL3, Matcher, get_char
+    DEFAULT_LEVEL1, DEFAULT_LEVEL2, DEFAULT_LEVEL3, Matcher, get_char,
 )
 from polyglot.builtins import iteritems
 
diff --git a/src/calibre/gui2/viewer/toolbars.py b/src/calibre/gui2/viewer/toolbars.py
index 5b358fcce5..aaa245b756 100644
--- a/src/calibre/gui2/viewer/toolbars.py
+++ b/src/calibre/gui2/viewer/toolbars.py
@@ -4,11 +4,10 @@
 
 import os
 from functools import partial
-
 from qt.core import (
-    QAction, QGroupBox, QHBoxLayout, QIcon, QKeySequence, QLabel, QListWidget,
-    QListWidgetItem, QMenu, Qt, QToolBar, QToolButton, QVBoxLayout, pyqtSignal, QDialog,
-    QAbstractItemView, QDialogButtonBox
+    QAbstractItemView, QAction, QDialog, QDialogButtonBox, QGroupBox, QHBoxLayout,
+    QIcon, QKeySequence, QLabel, QListWidget, QListWidgetItem, QMenu, Qt, QToolBar,
+    QToolButton, QVBoxLayout, pyqtSignal,
 )
 from qt.webengine import QWebEnginePage
 
@@ -18,6 +17,7 @@ from calibre.gui2.viewer.config import get_session_pref
 from calibre.gui2.viewer.shortcuts import index_to_key_sequence
 from calibre.gui2.viewer.web_view import set_book_path, vprefs
 from calibre.gui2.widgets2 import Dialog
+from calibre.startup import connect_lambda
 from calibre.utils.icu import primary_sort_key
 
 
@@ -236,7 +236,7 @@ class ActionsToolBar(ToolBar):
             a.setToolTip(_('Switch to paged mode -- where the text is broken into pages'))
 
     def change_sleep_permission(self, disallow_sleep=True):
-        from .control_sleep import prevent_sleep, allow_sleep
+        from .control_sleep import allow_sleep, prevent_sleep
         if disallow_sleep:
             if self.prevent_sleep_cookie is None:
                 try:
diff --git a/src/calibre/gui2/viewer/ui.py b/src/calibre/gui2/viewer/ui.py
index 5a764ba63f..2cebb9d851 100644
--- a/src/calibre/gui2/viewer/ui.py
+++ b/src/calibre/gui2/viewer/ui.py
@@ -10,8 +10,8 @@ from collections import defaultdict, namedtuple
 from hashlib import sha256
 from qt.core import (
     QApplication, QCursor, QDockWidget, QEvent, QMainWindow, QMenu, QMimeData,
-    QModelIndex, QPixmap, Qt, QTimer, QToolBar, QUrl, QVBoxLayout, QWidget,
-    pyqtSignal, sip
+    QModelIndex, QPixmap, Qt, QTimer, QToolBar, QUrl, QVBoxLayout, QWidget, pyqtSignal,
+    sip,
 )
 from threading import Thread
 
@@ -20,23 +20,23 @@ from calibre.constants import ismacos, iswindows
 from calibre.customize.ui import available_input_formats
 from calibre.db.annotations import merge_annotations
 from calibre.gui2 import (
-    add_to_recent_docs, choose_files, error_dialog, sanitize_env_vars
+    add_to_recent_docs, choose_files, error_dialog, sanitize_env_vars,
 )
 from calibre.gui2.dialogs.drm_error import DRMErrorMessage
 from calibre.gui2.image_popup import ImagePopup
 from calibre.gui2.main_window import MainWindow
 from calibre.gui2.viewer import get_current_book_data, performance_monitor
 from calibre.gui2.viewer.annotations import (
-    AnnotationsSaveWorker, annotations_dir, parse_annotations
+    AnnotationsSaveWorker, annotations_dir, parse_annotations,
 )
 from calibre.gui2.viewer.bookmarks import BookmarkManager
 from calibre.gui2.viewer.config import (
-    get_session_pref, load_reading_rates, save_reading_rates, vprefs
+    get_session_pref, load_reading_rates, save_reading_rates, vprefs,
 )
 from calibre.gui2.viewer.convert_book import clean_running_workers, prepare_book
 from calibre.gui2.viewer.highlights import HighlightsPanel
 from calibre.gui2.viewer.integration import (
-    get_book_library_details, load_annotations_map_from_library
+    get_book_library_details, load_annotations_map_from_library,
 )
 from calibre.gui2.viewer.lookup import Lookup
 from calibre.gui2.viewer.overlay import LoadingOverlay
@@ -44,6 +44,7 @@ from calibre.gui2.viewer.search import SearchPanel
 from calibre.gui2.viewer.toc import TOC, TOCSearch, TOCView
 from calibre.gui2.viewer.toolbars import ActionsToolBar
 from calibre.gui2.viewer.web_view import WebView, get_path_for_name, set_book_path
+from calibre.startup import connect_lambda
 from calibre.utils.date import utcnow
 from calibre.utils.img import image_from_path
 from calibre.utils.ipc.simple_worker import WorkerError
diff --git a/src/calibre/gui2/widgets.py b/src/calibre/gui2/widgets.py
index ae00f6feb1..d4766439d0 100644
--- a/src/calibre/gui2/widgets.py
+++ b/src/calibre/gui2/widgets.py
@@ -3,25 +3,28 @@ __copyright__ = '2008, Kovid Goyal <kovid at kovidgoyal.net>'
 '''
 Miscellaneous widgets used in the GUI
 '''
-import re, os
+import os
+import re
+from qt.core import (
+    QAction, QApplication, QClipboard, QColor, QComboBox, QCompleter, QCursor, QEvent,
+    QFont, QGraphicsScene, QGraphicsView, QIcon, QKeySequence, QLabel, QLineEdit,
+    QListWidget, QListWidgetItem, QMenu, QPageSize, QPainter, QPalette, QPen, QPixmap,
+    QPrinter, QRect, QSize, QSplitter, QSplitterHandle, QStringListModel,
+    QSyntaxHighlighter, Qt, QTextCharFormat, QTimer, QToolButton, QWidget, pyqtSignal,
+)
 
-from qt.core import (QIcon, QFont, QLabel, QListWidget, QAction, QEvent,
-        QListWidgetItem, QTextCharFormat, QApplication, QSyntaxHighlighter,
-        QCursor, QColor, QWidget, QPixmap, QSplitterHandle, QToolButton,
-        Qt, pyqtSignal, QSize, QSplitter, QPainter, QPageSize, QPrinter,
-        QLineEdit, QComboBox, QPen, QGraphicsScene, QMenu, QStringListModel, QKeySequence,
-        QCompleter, QTimer, QRect, QGraphicsView, QPalette, QClipboard)
-
-from calibre.constants import iswindows, ismacos
-from calibre.gui2 import (error_dialog, pixmap_to_data, gprefs,
-        warning_dialog)
-from calibre.gui2.filename_pattern_ui import Ui_Form
-from calibre import fit_image, strftime, force_unicode
+from calibre import fit_image, force_unicode, strftime
+from calibre.constants import ismacos, iswindows
 from calibre.ebooks import BOOK_EXTENSIONS
-from calibre.utils.config import prefs, XMLConfig
+from calibre.gui2 import error_dialog, gprefs, pixmap_to_data, warning_dialog
+from calibre.gui2.dnd import (
+    DownloadDialog, dnd_get_files, dnd_get_image, dnd_get_local_image_and_pixmap,
+    dnd_has_extension, dnd_has_image, image_extensions,
+)
+from calibre.gui2.filename_pattern_ui import Ui_Form
 from calibre.gui2.progress_indicator import ProgressIndicator as _ProgressIndicator
-from calibre.gui2.dnd import (dnd_has_image, dnd_get_image, dnd_get_files,
-    image_extensions, dnd_has_extension, dnd_get_local_image_and_pixmap, DownloadDialog)
+from calibre.startup import connect_lambda
+from calibre.utils.config import XMLConfig, prefs
 from calibre.utils.localization import localize_user_manual_link
 from polyglot.builtins import native_string_type
 
diff --git a/src/calibre/startup.py b/src/calibre/startup.py
index 5e92a98d82..4e31a9c6af 100644
--- a/src/calibre/startup.py
+++ b/src/calibre/startup.py
@@ -42,6 +42,24 @@ def get_debug_executable():
     return [exe_name]
 
 
+def connect_lambda(bound_signal, self, func, **kw):
+    import weakref
+    r = weakref.ref(self)
+    del self
+    num_args = func.__code__.co_argcount - 1
+    if num_args < 0:
+        raise TypeError('lambda must take at least one argument')
+
+    def slot(*args):
+        ctx = r()
+        if ctx is not None:
+            if len(args) != num_args:
+                args = args[:num_args]
+            func(ctx, *args)
+
+    bound_signal.connect(slot, **kw)
+
+
 def initialize_calibre():
     if hasattr(initialize_calibre, 'initialized'):
         return
@@ -126,22 +144,6 @@ def initialize_calibre():
     builtins.__dict__['icu_upper'] = icu_upper
     builtins.__dict__['icu_title'] = title_case
 
-    def connect_lambda(bound_signal, self, func, **kw):
-        import weakref
-        r = weakref.ref(self)
-        del self
-        num_args = func.__code__.co_argcount - 1
-        if num_args < 0:
-            raise TypeError('lambda must take at least one argument')
-
-        def slot(*args):
-            ctx = r()
-            if ctx is not None:
-                if len(args) != num_args:
-                    args = args[:num_args]
-                func(ctx, *args)
-
-        bound_signal.connect(slot, **kw)
     builtins.__dict__['connect_lambda'] = connect_lambda
 
     if islinux or ismacos or isfreebsd: