pythongh-109653: Defer importing warnings in several modules (python#110286)

Author: AlexWaygood

Lib/argparse.py

@@ -89,8 +89,6 @@
 import re as _re
 import sys as _sys
 
-import warnings
-
 from gettext import gettext as _, ngettext
 
 SUPPRESS = '==SUPPRESS=='
@@ -910,6 +908,7 @@ def __init__(self,
         #   parser.add_argument('-f', action=BooleanOptionalAction, type=int)
         for field_name in ('type', 'choices', 'metavar'):
             if locals()[field_name] is not _deprecated_default:
+                import warnings
                 warnings._deprecated(
                     field_name,
                     "{name!r} is deprecated as of Python 3.12 and will be "
@@ -1700,6 +1699,7 @@ def _remove_action(self, action):
         self._group_actions.remove(action)
 
     def add_argument_group(self, *args, **kwargs):
+        import warnings
         warnings.warn(
             "Nesting argument groups is deprecated.",
             category=DeprecationWarning,
@@ -1728,6 +1728,7 @@ def _remove_action(self, action):
         self._group_actions.remove(action)
 
     def add_mutually_exclusive_group(self, *args, **kwargs):
+        import warnings
         warnings.warn(
             "Nesting mutually exclusive groups is deprecated.",
             category=DeprecationWarning,

Lib/calendar.py

@@ -10,7 +10,6 @@
 from enum import IntEnum, global_enum
 import locale as _locale
 from itertools import repeat
-import warnings
 
 __all__ = ["IllegalMonthError", "IllegalWeekdayError", "setfirstweekday",
            "firstweekday", "isleap", "leapdays", "weekday", "monthrange",
@@ -44,6 +43,7 @@ def __str__(self):
 
 def __getattr__(name):
     if name in ('January', 'February'):
+        import warnings
         warnings.warn(f"The '{name}' attribute is deprecated, use '{name.upper()}' instead",
                       DeprecationWarning, stacklevel=2)
         if name == 'January':

Lib/getpass.py

@@ -18,7 +18,6 @@
 import io
 import os
 import sys
-import warnings
 
 __all__ = ["getpass","getuser","GetPassWarning"]
 
@@ -118,6 +117,7 @@ def win_getpass(prompt='Password: ', stream=None):
 
 
 def fallback_getpass(prompt='Password: ', stream=None):
+    import warnings
     warnings.warn("Can not control echo on the terminal.", GetPassWarning,
                   stacklevel=2)
     if not stream:

Lib/shutil.py

@@ -10,7 +10,6 @@
 import fnmatch
 import collections
 import errno
-import warnings
 
 try:
     import zlib
@@ -723,6 +722,7 @@ def rmtree(path, ignore_errors=False, onerror=None, *, onexc=None, dir_fd=None):
     """
 
     if onerror is not None:
+        import warnings
         warnings.warn("onerror argument is deprecated, use onexc instead",
                       DeprecationWarning, stacklevel=2)
 

Lib/tarfile.py

@@ -46,7 +46,6 @@
 import struct
 import copy
 import re
-import warnings
 
 try:
     import pwd
@@ -2219,6 +2218,7 @@ def _get_filter_function(self, filter):
         if filter is None:
             filter = self.extraction_filter
             if filter is None:
+                import warnings
                 warnings.warn(
                     'Python 3.14 will, by default, filter extracted tar '
                     + 'archives and reject files or modify their metadata. '

Misc/NEWS.d/next/Library/2023-10-03-15-17-03.gh-issue-109653.9DYOMD.rst

@@ -0,0 +1,3 @@
+Slightly improve the import time of several standard-library modules by
+deferring imports of :mod:`warnings` within those modules. Patch by Alex
+Waygood.