gh-118761: Improve import time by lazy import of warnings

Lib/codeop.py

@@ -33,7 +33,6 @@
 """
 
 import __future__
-import warnings
 
 _features = [getattr(__future__, fname)
              for fname in __future__.all_feature_names]
@@ -47,15 +46,18 @@
 PyCF_ONLY_AST = 0x400
 PyCF_ALLOW_INCOMPLETE_INPUT = 0x4000
 
+
 def _maybe_compile(compiler, source, filename, symbol):
     # Check for source consisting of only blank lines and comments.
     for line in source.split("\n"):
         line = line.strip()
-        if line and line[0] != '#':
-            break               # Leave it alone.
+        if line and line[0] != "#":
+            break  # Leave it alone.
     else:
         if symbol != "eval":
-            source = "pass"     # Replace it with a 'pass' statement
+            source = "pass"  # Replace it with a 'pass' statement
+
+    import warnings
 
     # Disable compiler warnings when checking for incomplete input.
     with warnings.catch_warnings():
@@ -74,13 +76,15 @@ def _maybe_compile(compiler, source, filename, symbol):
 
     return compiler(source, filename, symbol, incomplete_input=False)
 
+
 def _compile(source, filename, symbol, incomplete_input=True):
     flags = 0
     if incomplete_input:
         flags |= PyCF_ALLOW_INCOMPLETE_INPUT
         flags |= PyCF_DONT_IMPLY_DEDENT
     return compile(source, filename, symbol, flags)
 
+
 def compile_command(source, filename="<input>", symbol="single"):
     r"""Compile a command and determine whether it is incomplete.
 
@@ -102,17 +106,19 @@ def compile_command(source, filename="<input>", symbol="single"):
     """
     return _maybe_compile(_compile, source, filename, symbol)
 
+
 class Compile:
     """Instances of this class behave much like the built-in compile
     function, but if one is used to compile text containing a future
     statement, it "remembers" and compiles all subsequent program texts
     with the statement in force."""
+
     def __init__(self):
         self.flags = PyCF_DONT_IMPLY_DEDENT | PyCF_ALLOW_INCOMPLETE_INPUT
 
     def __call__(self, source, filename, symbol, flags=0, **kwargs):
         flags |= self.flags
-        if kwargs.get('incomplete_input', True) is False:
+        if kwargs.get("incomplete_input", True) is False:
             flags &= ~PyCF_DONT_IMPLY_DEDENT
             flags &= ~PyCF_ALLOW_INCOMPLETE_INPUT
         codeob = compile(source, filename, symbol, flags, True)
@@ -123,6 +129,7 @@ def __call__(self, source, filename, symbol, flags=0, **kwargs):
                 self.flags |= feature.compiler_flag
         return codeob
 
+
 class CommandCompiler:
     """Instances of this class have __call__ methods identical in
     signature to compile_command; the difference is that if the

Lib/ctypes/_layout.py

@@ -5,8 +5,6 @@
 """
 
 import sys
-import warnings
-import struct
 
 from _ctypes import CField, buffer_info
 import ctypes

Lib/hmac.py

@@ -3,7 +3,6 @@
 Implements the HMAC algorithm as described by RFC 2104.
 """
 
-import warnings as _warnings
 try:
     import _hashlib as _hashopenssl
 except ImportError:
@@ -31,9 +30,7 @@ class HMAC:
     """
     blocksize = 64  # 512-bit HMAC; can be changed in subclasses.
 
-    __slots__ = (
-        "_hmac", "_inner", "_outer", "block_size", "digest_size"
-    )
+    __slots__ = ("_hmac", "_inner", "_outer", "block_size", "digest_size")
 
     def __init__(self, key, msg=None, digestmod=''):
         """Create a new HMAC object.
@@ -81,15 +78,17 @@ def _init_old(self, key, msg, digestmod):
         self._inner = digest_cons()
         self.digest_size = self._inner.digest_size
 
+        import warnings
+
         if hasattr(self._inner, 'block_size'):
             blocksize = self._inner.block_size
             if blocksize < 16:
-                _warnings.warn('block_size of %d seems too small; using our '
+                warnings.warn('block_size of %d seems too small; using our '
                                'default of %d.' % (blocksize, self.blocksize),
                                RuntimeWarning, 2)
                 blocksize = self.blocksize
         else:
-            _warnings.warn('No block_size attribute on given digest object; '
+            warnings.warn('No block_size attribute on given digest object; '
                            'Assuming %d.' % (self.blocksize),
                            RuntimeWarning, 2)
             blocksize = self.blocksize

Lib/importlib/_bootstrap_external.py

@@ -26,7 +26,6 @@
 import _imp
 import _io
 import sys
-import _warnings
 import marshal
 
 
@@ -259,6 +258,7 @@ def cache_from_source(path, debug_override=None, *, optimization=None):
 
     """
     if debug_override is not None:
+        import _warnings
         _warnings.warn('the debug_override parameter is deprecated; use '
                        "'optimization' instead", DeprecationWarning)
         if optimization is not None:
@@ -663,13 +663,15 @@ def _bless_my_loader(module_globals):
         if loader is None:
             exc = AttributeError if spec_loader is missing else ValueError
             raise exc('Module globals is missing a __spec__.loader')
+        import _warnings
         _warnings.warn(
             'Module globals is missing a __spec__.loader',
             DeprecationWarning)
         spec_loader = loader
 
     assert spec_loader is not None
     if loader is not None and loader != spec_loader:
+        import _warnings
         _warnings.warn(
             'Module globals; __loader__ != __spec__.loader',
             DeprecationWarning)
@@ -716,6 +718,7 @@ def _search_registry(cls, fullname):
 
     @classmethod
     def find_spec(cls, fullname, path=None, target=None):
+        import _warnings
         _warnings.warn('importlib.machinery.WindowsRegistryFinder is '
                        'deprecated; use site configuration instead. '
                        'Future versions of Python may not enable this '
@@ -1224,6 +1227,7 @@ def invalidate_caches():
     def _path_hooks(path):
         """Search sys.path_hooks for a finder for 'path'."""
         if sys.path_hooks is not None and not sys.path_hooks:
+            import _warnings
             _warnings.warn('sys.path_hooks is empty', ImportWarning)
         for hook in sys.path_hooks:
             try:

Lib/importlib/metadata/__init__.py

@@ -12,7 +12,6 @@
 import zipfile
 import operator
 import textwrap
-import warnings
 import functools
 import itertools
 import posixpath
@@ -341,6 +340,7 @@ def __new__(cls, *args, **kwargs):
             if getattr(getattr(cls, name), '__isabstractmethod__', False)
         }
         if abstract:
+            import warnings
             warnings.warn(
                 f"Unimplemented abstract methods {abstract}",
                 DeprecationWarning,

Lib/importlib/resources/_common.py

@@ -6,7 +6,6 @@
 import types
 import importlib
 import inspect
-import warnings
 import itertools
 
 from typing import Union, Optional, cast
@@ -35,6 +34,7 @@ def wrapper(anchor=undefined, package=undefined):
         if package is not undefined:
             if anchor is not undefined:
                 return func(anchor, package)
+            import warnings
             warnings.warn(
                 "First parameter to files is renamed to 'anchor'",
                 DeprecationWarning,

Lib/importlib/resources/_functional.py

@@ -1,7 +1,5 @@
 """Simplified function-based API for importlib.resources"""
 
-import warnings
-
 from ._common import files, as_file
 
 
@@ -51,6 +49,7 @@ def contents(anchor, *path_names):
     The iterable returns :class:`str` resources (e.g. files).
     The iterable does not recurse into subdirectories.
     """
+    import warnings
     warnings.warn(
         "importlib.resources.contents is deprecated. "
         "Use files(anchor).iterdir() instead.",

Lib/importlib/resources/readers.py

@@ -6,7 +6,6 @@
 import pathlib
 import operator
 import re
-import warnings
 import zipfile
 from collections.abc import Iterator
 
@@ -194,6 +193,7 @@ def _ensure_traversable(path):
     if not isinstance(path, str):
         return path
 
+    import warnings
     warnings.warn(
         "String arguments are deprecated. Pass a Traversable instead.",
         DeprecationWarning,

Lib/logging/__init__.py

@@ -23,7 +23,7 @@
 To use, simply 'import logging' and log away!
 """
 
-import sys, os, time, io, re, traceback, warnings, weakref, collections.abc
+import sys, os, time, io, re, traceback, weakref, collections.abc
 
 from types import GenericAlias
 from string import Template
@@ -1531,6 +1531,7 @@ def warning(self, msg, *args, **kwargs):
             self._log(WARNING, msg, args, **kwargs)
 
     def warn(self, msg, *args, **kwargs):
+        import warnings
         warnings.warn("The 'warn' method is deprecated, "
             "use 'warning' instead", DeprecationWarning, 2)
         self.warning(msg, *args, **kwargs)
@@ -1912,6 +1913,7 @@ def warning(self, msg, *args, **kwargs):
         self.log(WARNING, msg, *args, **kwargs)
 
     def warn(self, msg, *args, **kwargs):
+        import warnings
         warnings.warn("The 'warn' method is deprecated, "
             "use 'warning' instead", DeprecationWarning, 2)
         self.warning(msg, *args, **kwargs)
@@ -2180,6 +2182,7 @@ def warning(msg, *args, **kwargs):
     root.warning(msg, *args, **kwargs)
 
 def warn(msg, *args, **kwargs):
+    import warnings
     warnings.warn("The 'warn' function is deprecated, "
         "use 'warning' instead", DeprecationWarning, 2)
     warning(msg, *args, **kwargs)
@@ -2299,6 +2302,7 @@ def _showwarning(message, category, filename, lineno, file=None, line=None):
         if _warnings_showwarning is not None:
             _warnings_showwarning(message, category, filename, lineno, file, line)
     else:
+        import warnings
         s = warnings.formatwarning(message, category, filename, lineno, line)
         logger = getLogger("py.warnings")
         if not logger.handlers:
@@ -2316,9 +2320,11 @@ def captureWarnings(capture):
     global _warnings_showwarning
     if capture:
         if _warnings_showwarning is None:
+            import warnings
             _warnings_showwarning = warnings.showwarning
             warnings.showwarning = _showwarning
     else:
         if _warnings_showwarning is not None:
+            import warnings
             warnings.showwarning = _warnings_showwarning
             _warnings_showwarning = None

Lib/pkgutil.py

@@ -8,8 +8,6 @@
 import os
 import os.path
 import sys
-from types import ModuleType
-import warnings
 
 __all__ = [
     'get_importer', 'iter_importers',

Lib/pydoc.py

@@ -71,7 +71,6 @@ class or function within a module or module in a package.  If the
 import time
 import tokenize
 import urllib.parse
-import warnings
 from annotationlib import Format
 from collections import deque
 from reprlib import Repr
@@ -376,6 +375,7 @@ def sort_attributes(attrs, object):
 
 def ispackage(path):
     """Guess whether a path refers to a package directory."""
+    import warnings
     warnings.warn('The pydoc.ispackage() function is deprecated',
                   DeprecationWarning, stacklevel=2)
     if os.path.isdir(path):
@@ -394,6 +394,7 @@ def source_synopsis(file):
             if tok_type == tokenize.STRING:
                 string += tok_string
             elif tok_type == tokenize.NEWLINE:
+                import warnings
                 with warnings.catch_warnings():
                     # Ignore the "invalid escape sequence" warning.
                     warnings.simplefilter("ignore", SyntaxWarning)
@@ -457,6 +458,7 @@ def __init__(self, filename, exc_info):
             self.value = exc_info
             self.tb = exc_info.__traceback__
         else:
+            import warnings
             warnings.warn("A tuple value for exc_info is deprecated, use an exception instance",
                           DeprecationWarning)
 
@@ -2294,6 +2296,7 @@ def callback(path, modname, desc):
         print(modname, desc and '- ' + desc)
     def onerror(modname):
         pass
+    import warnings
     with warnings.catch_warnings():
         warnings.filterwarnings('ignore') # ignore problems during import
         ModuleScanner().run(callback, key, onerror=onerror)
@@ -2543,6 +2546,7 @@ def callback(path, modname, desc):
                 modname = modname[:-9] + ' (package)'
             search_result.append((modname, desc and '- ' + desc))
 
+        import warnings
         with warnings.catch_warnings():
             warnings.filterwarnings('ignore') # ignore problems during import
             def onerror(modname):

Lib/rlcompleter.py

@@ -35,12 +35,12 @@
 import keyword
 import re
 import __main__
-import warnings
 
 __all__ = ["Completer"]
 
+
 class Completer:
-    def __init__(self, namespace = None):
+    def __init__(self, namespace=None):
         """Create a new completer for the command line.
 
         Completer([namespace]) -> completer instance.
@@ -89,6 +89,7 @@ def complete(self, text, state):
                 return None
 
         if state == 0:
+            import warnings
             with warnings.catch_warnings(action="ignore"):
                 if "." in text:
                     self.matches = self.attr_matches(text)