[3.12] gh-112346: Document the OS byte in `gzip.compress` output change in 3.11 (GH-120480) by miss-islington · Pull Request #120613 · python/cpython
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@@ -768,6 +768,21 @@ functools
(Contributed by Yurii Karabas in :issue:`46014`.)
.. _whatsnew311-gzip:
gzip ----
* The :func:`gzip.compress` function is now faster when used with the **mtime=0** argument as it delegates the compression entirely to a single :func:`zlib.compress` operation. There is one side effect of this change: The gzip file header contains an "OS" byte in its header. That was traditionally always set to a value of 255 representing "unknown" by the :mod:`gzip` module. Now, when using :func:`~gzip.compress` with **mtime=0**, it may be set to a different value by the underlying zlib C library Python was linked against. (See :gh:`112346` for details on the side effect.)
.. _whatsnew311-hashlib:
hashlib Expand Down
.. _whatsnew311-gzip:
gzip ----
* The :func:`gzip.compress` function is now faster when used with the **mtime=0** argument as it delegates the compression entirely to a single :func:`zlib.compress` operation. There is one side effect of this change: The gzip file header contains an "OS" byte in its header. That was traditionally always set to a value of 255 representing "unknown" by the :mod:`gzip` module. Now, when using :func:`~gzip.compress` with **mtime=0**, it may be set to a different value by the underlying zlib C library Python was linked against. (See :gh:`112346` for details on the side effect.)
.. _whatsnew311-hashlib:
hashlib Expand Down