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mtime is None for writable GzipFile instances #160860

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mtime is None for writable GzipFile instances#160860
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stdlibStandard Library Python modules in the Lib/ directorytype-bugAn unexpected behavior, bug, or error

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@jepler
jepler
opened on Oct 29, 2026

Bug report

>>> g = gzip.open(io.BytesIO(), mtime=1234567)
>>> print(g.mtime)
None

Instead of being None, I believe it should reflect the value passed to the constructor.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

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  1. jepler
    added
    type-bugAn unexpected behavior, bug, or error
    on Oct 29, 2026
  2. jepler
    added a commit that references this issue on Oct 29, 2026

    pythongh-160860: Fix value of GzipFIle.mtime of writable stream

    1c817f9
  3. NekoAsakura
    added
    stdlibStandard Library Python modules in the Lib/ directory
    on Oct 29, 2026
  4. aisk
    added this to Compression issues 🗜on Oct 29, 2026
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