Bug report
Bug description:
The threading module defines local as follows:
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try: |
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from _thread import _local as local |
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except ImportError: |
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from _threading_local import local |
But _threading_local also uses threading as follows:
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from threading import current_thread, RLock |
This was fine at first, since threading never used thread-local data (the import was near the end). However, this changed in gh-114424:
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# Helper thread-local instance to detect when a _DummyThread |
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# is collected. Not a part of the public API. |
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_thread_local_info = local() |
The _threading_local.local object depends on threading.current_thread(), and this dependency occurs when the object is created:
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# We need to create the thread dict in anticipation of |
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# __init__ being called, to make sure we don't call it |
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# again ourselves. |
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impl.create_dict() |
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def create_dict(self): |
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"""Create a new dict for the current thread, and return it.""" |
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localdict = {} |
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key = self.key |
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thread = current_thread() |
The object is created (and local is imported) before current_thread() is defined. As a result, there is the broken circular import, which can be reproduced as follows:
>>> import _thread
>>> del _thread._local
>>> import threading
Traceback (most recent call last):
File "/home/user/.local/share/mise/installs/python/3.14.7/lib/python3.14/threading.py", line 67, in <module>
from _thread import _local as local
ImportError: cannot import name '_local' from '_thread' (unknown location)
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "<python-input-2>", line 1, in <module>
import threading
File "/home/user/.local/share/mise/installs/python/3.14.7/lib/python3.14/threading.py", line 69, in <module>
from _threading_local import local
File "/home/user/.local/share/mise/installs/python/3.14.7/lib/python3.14/_threading_local.py", line 120, in <module>
from threading import current_thread, RLock
ImportError: cannot import name 'current_thread' from partially initialized module 'threading' (most likely due to a circular import) (/home/user/.local/share/mise/installs/python/3.14.7/lib/python3.14/threading.py)Since the issue has not been reported before, this raises a legitimate question: is the fallback still relevant?
Related: #141460.
CPython versions tested on:
3.13, 3.14
Operating systems tested on:
Linux
Bug report
Bug description:
The threading module defines local as follows:
cpython/Lib/threading.py
Lines 67 to 70 in ee521e8
But _threading_local also uses threading as follows:
cpython/Lib/_threading_local.py
Line 120 in ee521e8
This was fine at first, since threading never used thread-local data (the import was near the end). However, this changed in gh-114424:
cpython/Lib/threading.py
Lines 1540 to 1542 in ee521e8
The _threading_local.local object depends on threading.current_thread(), and this dependency occurs when the object is created:
cpython/Lib/_threading_local.py
Lines 93 to 96 in ee521e8
cpython/Lib/_threading_local.py
Lines 42 to 46 in ee521e8
The object is created (and local is imported) before current_thread() is defined. As a result, there is the broken circular import, which can be reproduced as follows:
Since the issue has not been reported before, this raises a legitimate question: is the fallback still relevant?
Related: #141460.
CPython versions tested on:
3.13, 3.14
Operating systems tested on:
Linux