diff --git a/Lib/string.py b/Lib/string.py index c4f05c7223ce8a..eab5067c9b133e 100644 --- a/Lib/string.py +++ b/Lib/string.py @@ -49,11 +49,18 @@ def capwords(s, sep=None): #################################################################### -import re as _re -from collections import ChainMap as _ChainMap - _sentinel_dict = {} + +class _TemplatePattern: + # This descriptor is overwritten in ``Template._compile_pattern()``. + def __get__(self, instance, cls=None): + if cls is None: + return self + return cls._compile_pattern() +_TemplatePattern = _TemplatePattern() + + class Template: """A string class for supporting $-substitutions.""" @@ -64,14 +71,21 @@ class Template: # See https://bugs.python.org/issue31672 idpattern = r'(?a:[_a-z][_a-z0-9]*)' braceidpattern = None - flags = _re.IGNORECASE + flags = None # default: re.IGNORECASE + + pattern = _TemplatePattern # use a descriptor to compile the pattern def __init_subclass__(cls): super().__init_subclass__() - if 'pattern' in cls.__dict__: - pattern = cls.pattern - else: - delim = _re.escape(cls.delimiter) + cls._compile_pattern() + + @classmethod + def _compile_pattern(cls): + import re # deferred import, for performance + + pattern = cls.__dict__.get('pattern', _TemplatePattern) + if pattern is _TemplatePattern: + delim = re.escape(cls.delimiter) id = cls.idpattern bid = cls.braceidpattern or cls.idpattern pattern = fr""" @@ -82,7 +96,10 @@ def __init_subclass__(cls): (?P) # Other ill-formed delimiter exprs ) """ - cls.pattern = _re.compile(pattern, cls.flags | _re.VERBOSE) + if cls.flags is None: + cls.flags = re.IGNORECASE + pat = cls.pattern = re.compile(pattern, cls.flags | re.VERBOSE) + return pat def __init__(self, template): self.template = template @@ -105,7 +122,8 @@ def substitute(self, mapping=_sentinel_dict, /, **kws): if mapping is _sentinel_dict: mapping = kws elif kws: - mapping = _ChainMap(kws, mapping) + from collections import ChainMap + mapping = ChainMap(kws, mapping) # Helper function for .sub() def convert(mo): # Check the most common path first. @@ -124,7 +142,8 @@ def safe_substitute(self, mapping=_sentinel_dict, /, **kws): if mapping is _sentinel_dict: mapping = kws elif kws: - mapping = _ChainMap(kws, mapping) + from collections import ChainMap + mapping = ChainMap(kws, mapping) # Helper function for .sub() def convert(mo): named = mo.group('named') or mo.group('braced') @@ -170,10 +189,6 @@ def get_identifiers(self): self.pattern) return ids -# Initialize Template.pattern. __init_subclass__() is automatically called -# only for subclasses, not for the Template class itself. -Template.__init_subclass__() - ######################################################################## # the Formatter class diff --git a/Misc/NEWS.d/next/Library/2025-04-03-01-35-02.gh-issue-118761.VQcj70.rst b/Misc/NEWS.d/next/Library/2025-04-03-01-35-02.gh-issue-118761.VQcj70.rst new file mode 100644 index 00000000000000..257ad7ece7d18a --- /dev/null +++ b/Misc/NEWS.d/next/Library/2025-04-03-01-35-02.gh-issue-118761.VQcj70.rst @@ -0,0 +1,2 @@ +Improve import times by up to 27x for the :mod:`string` module. +Patch by Adam Turner. pFad - Phonifier reborn

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