Eryk Sun <eryk...@gmail.com> added the comment:
Your example uses delete=False. In Windows, the provision about reopening the
file while it's open applies to delete=True. With the latter, the file is
opened with the O_TEMPORARY flag. At the OS level, this flag modifies the
CreateFileW() call as follows:
dwDesiredAccess |= DELETE;
dwShareMode |= FILE_SHARE_DELETE;
dwFlagsAndAttributes |= FILE_FLAG_DELETE_ON_CLOSE;
Because the open has delete access, which it shares, it can be opened again
only if the open shares delete access. An open that doesn't share delete access
will fail with a sharing violation. It can be reopened with os.open() with the
O_TEMPORARY flag, since this shares delete access. But Python's builtin open()
does not share delete access, and neither do most other programs with which one
might want to reopen the file.
This behavior is limiting to the point of making NamedTemporaryFile()
practically useless in Windows with delete=True. There is an ongoing discussion
about redesigning NamedTemporaryFile() to never use O_TEMPORARY in Windows.
----------
nosy: +eryksun
type: -> enhancement
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue44055>
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