Eryk Sun <eryk...@gmail.com> added the comment:
> I don't know enough about when and why CPython decides to
> replace .pyc files
It's straight-forward in the case of py_compile.compile():
>>> pyc = py_compile.compile('test.py')
>>> f = open(pyc)
>>> try: py_compile.compile('test.py')
... except OSError as e: print(e)
...
[WinError 5] Access is denied:
'__pycache__\\test.cpython-310.pyc.1914201873840' ->
'__pycache__\\test.cpython-310.pyc'
Rewriting the file uses `importlib._bootstrap_external._write_atomic()`, which
writes the PYC to a temporary name and then tries to replace the existing file
via os.replace().
Replacing an existing filename will fail with access denied in Windows if the
target filename exists and is already open, mapped as image/data, readonly, or
a directory. Notably it's not a sharing violation in the case of an open file,
which means it doesn't matter whether the open(s) share delete access or not.
In Windows 10 the NT API has a new file rename operation that supports a flag
to replace an open file, but in this case we're still stuck with the problem
that existing opens have to share delete access. Most opens could share delete
access without a problem, but most don't.
----------
components: +Windows
nosy: +eryksun, paul.moore, steve.dower, tim.golden, zach.ware
versions: +Python 3.10, Python 3.11
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<https://bugs.python.org/issue37387>
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