bpo-28286: Deprecate opening GzipFile for writing implicitly. (GH-16417)

Always specify the mode argument for writing.
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Serhiy Storchaka 2019-11-16 18:56:57 +02:00 committed by GitHub
parent bd44a7ead9
commit a0652328a2
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5 changed files with 25 additions and 2 deletions

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@ -88,7 +88,8 @@ The module defines the following items:
The *mode* argument can be any of ``'r'``, ``'rb'``, ``'a'``, ``'ab'``, ``'w'``,
``'wb'``, ``'x'``, or ``'xb'``, depending on whether the file will be read or
written. The default is the mode of *fileobj* if discernible; otherwise, the
default is ``'rb'``.
default is ``'rb'``. In future Python releases the mode of *fileobj* will
not be used. It is better to always specify *mode* for writing.
Note that the file is always opened in binary mode. To open a compressed file
in text mode, use :func:`.open` (or wrap your :class:`GzipFile` with an
@ -164,6 +165,10 @@ The module defines the following items:
.. versionchanged:: 3.6
Accepts a :term:`path-like object`.
.. deprecated:: 3.9
Opening :class:`GzipFile` for writing without specifying the *mode*
argument is deprecated.
.. function:: compress(data, compresslevel=9, *, mtime=None)

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@ -239,6 +239,12 @@ Deprecated
the module will restrict its seeds to :const:`None`, :class:`int`,
:class:`float`, :class:`str`, :class:`bytes`, and :class:`bytearray`.
* Opening the :class:`~gzip.GzipFile` file for writing without specifying
the *mode* argument is deprecated. In future Python versions it will always
be opened for reading by default. Specify the *mode* argument for opening
it for writing and silencing a warning.
(Contributed by Serhiy Storchaka in :issue:`28286`.)
* Deprecated the ``split()`` method of :class:`_tkinter.TkappType` in
favour of the ``splitlist()`` method which has more consistent and
predicable behavior.

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@ -177,6 +177,7 @@ class GzipFile(_compression.BaseStream):
filename = ''
else:
filename = os.fspath(filename)
origmode = mode
if mode is None:
mode = getattr(fileobj, 'mode', 'rb')
@ -187,6 +188,13 @@ class GzipFile(_compression.BaseStream):
self.name = filename
elif mode.startswith(('w', 'a', 'x')):
if origmode is None:
import warnings
warnings.warn(
"GzipFile was opened for writing, but this will "
"change in future Python releases. "
"Specify the mode argument for opening it for writing.",
FutureWarning, 2)
self.mode = WRITE
self._init_write(filename)
self.compress = zlib.compressobj(compresslevel,

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@ -469,7 +469,9 @@ class TestGzip(BaseTest):
if "x" in mode:
support.unlink(self.filename)
with open(self.filename, mode) as f:
with gzip.GzipFile(fileobj=f) as g:
with self.assertWarns(FutureWarning):
g = gzip.GzipFile(fileobj=f)
with g:
self.assertEqual(g.mode, gzip.WRITE)
def test_bytes_filename(self):

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@ -0,0 +1,2 @@
Deprecate opening :class:`~gzip.GzipFile` for writing implicitly. Always
specify the *mode* argument for writing.