https://github.com/python/cpython/commit/4085ff7b32f91bad7d821e5564d8565c5928f7d1
commit: 4085ff7b32f91bad7d821e5564d8565c5928f7d1
branch: main
author: Savannah Ostrowski <[email protected]>
committer: savannahostrowski <[email protected]>
date: 2025-12-05T16:47:50Z
summary:
GH-142267: Cache formatter to avoid repeated `_set_color` calls (#142268)
files:
A Misc/NEWS.d/next/Library/2025-12-04-23-26-12.gh-issue-142267.yOM6fP.rst
M Lib/argparse.py
diff --git a/Lib/argparse.py b/Lib/argparse.py
index 41467707d393c0..10393b6a02b0be 100644
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -1568,8 +1568,8 @@ def add_argument(self, *args, **kwargs):
f'instance of it must be passed')
# raise an error if the metavar does not match the type
- if hasattr(self, "_get_formatter"):
- formatter = self._get_formatter()
+ if hasattr(self, "_get_validation_formatter"):
+ formatter = self._get_validation_formatter()
try:
formatter._format_args(action, None)
except TypeError:
@@ -1763,8 +1763,8 @@ def _handle_conflict_resolve(self, action,
conflicting_actions):
action.container._remove_action(action)
def _check_help(self, action):
- if action.help and hasattr(self, "_get_formatter"):
- formatter = self._get_formatter()
+ if action.help and hasattr(self, "_get_validation_formatter"):
+ formatter = self._get_validation_formatter()
try:
formatter._expand_help(action)
except (ValueError, TypeError, KeyError) as exc:
@@ -1919,6 +1919,9 @@ def __init__(self,
self.suggest_on_error = suggest_on_error
self.color = color
+ # Cached formatter for validation (avoids repeated _set_color calls)
+ self._cached_formatter = None
+
add_group = self.add_argument_group
self._positionals = add_group(_('positional arguments'))
self._optionals = add_group(_('options'))
@@ -2750,6 +2753,13 @@ def _get_formatter(self):
formatter._set_color(self.color)
return formatter
+ def _get_validation_formatter(self):
+ # Return cached formatter for read-only validation operations
+ # (_expand_help and _format_args). Avoids repeated slow _set_color
calls.
+ if self._cached_formatter is None:
+ self._cached_formatter = self._get_formatter()
+ return self._cached_formatter
+
# =====================
# Help-printing methods
# =====================
diff --git
a/Misc/NEWS.d/next/Library/2025-12-04-23-26-12.gh-issue-142267.yOM6fP.rst
b/Misc/NEWS.d/next/Library/2025-12-04-23-26-12.gh-issue-142267.yOM6fP.rst
new file mode 100644
index 00000000000000..f46e82105fc2f5
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-12-04-23-26-12.gh-issue-142267.yOM6fP.rst
@@ -0,0 +1 @@
+Improve :mod:`argparse` performance by caching the formatter used for argument
validation.
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