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GH-101362: Check pathlib.Path flavour compatibility at import time (G…
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…H-101664)

This saves a comparison in `pathlib.Path.__new__()` and reduces the time taken to run `Path()` by ~5%.

Automerge-Triggered-By: GH:AlexWaygood
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barneygale authored Mar 5, 2023
1 parent 3572c86 commit 3e60e02
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Showing 2 changed files with 13 additions and 5 deletions.
16 changes: 11 additions & 5 deletions Lib/pathlib.py
Original file line number Diff line number Diff line change
Expand Up @@ -707,11 +707,7 @@ def __new__(cls, *args, **kwargs):
warnings._deprecated("pathlib.PurePath(**kwargs)", msg, remove=(3, 14))
if cls is Path:
cls = WindowsPath if os.name == 'nt' else PosixPath
self = cls._from_parts(args)
if self._flavour is not os.path:
raise NotImplementedError("cannot instantiate %r on your system"
% (cls.__name__,))
return self
return cls._from_parts(args)

def _make_child_relpath(self, part):
# This is an optimization used for dir walking. `part` must be
Expand Down Expand Up @@ -1261,9 +1257,19 @@ class PosixPath(Path, PurePosixPath):
"""
__slots__ = ()

if os.name == 'nt':
def __new__(cls, *args, **kwargs):
raise NotImplementedError(
f"cannot instantiate {cls.__name__!r} on your system")

class WindowsPath(Path, PureWindowsPath):
"""Path subclass for Windows systems.
On a Windows system, instantiating a Path should return this object.
"""
__slots__ = ()

if os.name != 'nt':
def __new__(cls, *args, **kwargs):
raise NotImplementedError(
f"cannot instantiate {cls.__name__!r} on your system")
Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Speed up :class:`pathlib.Path` construction by running the path flavour
compatibility check only when pathlib is imported.

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