Open
Description
Bug report
Bug description:
This code behaves very differently on Python 3.13 than 3.12:
(p for p in pathlib.Path('does-not-exist').iterdir()) 🐚 py -3.12 -c "import pathlib; (p for p in pathlib.Path('does-not-exist').iterdir())"
🐚 py -3.13 -c "import pathlib; (p for p in pathlib.Path('does-not-exist').iterdir())"
Traceback (most recent call last):
File "<string>", line 1, in <module>
import pathlib; (p for p in pathlib.Path('does-not-exist').iterdir())
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
File "/opt/homebrew/Cellar/python@3.13/3.13.1/Frameworks/Python.framework/Versions/3.13/lib/python3.13/pathlib/_local.py", line 575, in iterdir
with os.scandir(root_dir) as scandir_it:
~~~~~~~~~~^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: 'does-not-exist'In Python 3.12, the generator expression was evaluated lazily, not invoking path.iterdir() until the generator was consumed. On 3.13, at least a portion of the generator is evaluated, triggering the exception when the dir does not exist.
I discovered this issue in jaraco/jaraco.develop#26.
I looked at What's New for Python 3.13, and there's only one mention of generator expressions regarding mutation of locals in generator expressions, which doesn't seem to be relevant here.
That change mentions #74929, so maybe that change is also implicated in the change in execution order.
CPython versions tested on:
3.13
Operating systems tested on:
macOS