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gh-91349: Adjust default compression level to 6 (down from 9) in gzip and tarfile#131470

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20 changes: 17 additions & 3 deletionsDoc/library/gzip.rst
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Expand Up@@ -26,7 +26,7 @@ Note that additional file formats which can be decompressed by the
The module defines the following items:


.. function:: open(filename, mode='rb', compresslevel=9, encoding=None, errors=None, newline=None)
.. function:: open(filename, mode='rb', compresslevel=6, encoding=None, errors=None, newline=None)

Open a gzip-compressed file in binary or text mode, returning a :term:`file
object`.
Expand DownExpand Up@@ -59,6 +59,11 @@ The module defines the following items:
.. versionchanged:: 3.6
Accepts a :term:`path-like object`.

.. versionchanged:: 3.14
The default compression level was reduced to 6 (down from 9).
It is the default level used by most compression tools and a better
tradeoff between speed and performance.

.. exception:: BadGzipFile

An exception raised for invalid gzip files. It inherits from :exc:`OSError`.
Expand All@@ -67,7 +72,7 @@ The module defines the following items:

.. versionadded:: 3.8

.. class:: GzipFile(filename=None, mode=None, compresslevel=9, fileobj=None, mtime=None)
.. class:: GzipFile(filename=None, mode=None, compresslevel=6, fileobj=None, mtime=None)

Constructor for the :class:`GzipFile` class, which simulates most of the
methods of a :term:`file object`, with the exception of the :meth:`~io.IOBase.truncate`
Expand DownExpand Up@@ -181,8 +186,13 @@ The module defines the following items:
Remove the ``filename`` attribute, use the :attr:`~GzipFile.name`
attribute instead.

.. versionchanged:: 3.14
The default compression level was reduced to 6 (down from 9).
It is the default level used by most compression tools and a better
tradeoff between speed and performance.

.. function:: compress(data, compresslevel=9, *, mtime=0)

.. function:: compress(data, compresslevel=6, *, mtime=0)

Compress the *data*, returning a :class:`bytes` object containing
the compressed data. *compresslevel* and *mtime* have the same meaning as in
Expand All@@ -206,6 +216,10 @@ The module defines the following items:
The *mtime* parameter now defaults to 0 for reproducible output.
For the previous behaviour of using the current time,
pass ``None`` to *mtime*.
.. versionchanged:: 3.14
The default compression level was reduced to 6 (down from 9).
It is the default level used by most compression tools and a better
tradeoff between speed and performance.

.. function:: decompress(data)

Expand Down
6 changes: 5 additions & 1 deletionDoc/library/tarfile.rst
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Expand Up@@ -110,7 +110,7 @@ Some facts and figures:

For modes ``'w:gz'``, ``'x:gz'``, ``'w|gz'``, ``'w:bz2'``, ``'x:bz2'``,
``'w|bz2'``, :func:`tarfile.open` accepts the keyword argument
*compresslevel* (default ``9``) to specify the compression level of the file.
*compresslevel* (default ``6``) to specify the compression level of the file.

For modes ``'w:xz'``, ``'x:xz'`` and ``'w|xz'``, :func:`tarfile.open` accepts the
keyword argument *preset* to specify the compression level of the file.
Expand DownExpand Up@@ -170,6 +170,10 @@ Some facts and figures:
.. versionchanged:: 3.14
The *preset* keyword argument also works for streams.

.. versionchanged:: 3.14
The default compression level was reduced to 6 (down from 9).
It is the default level used by most compression tools and a better
tradeoff between speed and performance.

.. class:: TarFile
:noindex:
Expand Down
6 changes: 3 additions & 3 deletionsLib/gzip.py
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Expand Up@@ -30,7 +30,7 @@
_WRITE_BUFFER_SIZE = 4 * io.DEFAULT_BUFFER_SIZE


def open(filename, mode="rb", compresslevel=_COMPRESS_LEVEL_BEST,
def open(filename, mode="rb", compresslevel=_COMPRESS_LEVEL_TRADEOFF,
encoding=None, errors=None, newline=None):
"""Open a gzip-compressed file in binary or text mode.

Expand DownExpand Up@@ -158,7 +158,7 @@ class GzipFile(_streams.BaseStream):
myfileobj = None

def __init__(self, filename=None, mode=None,
compresslevel=_COMPRESS_LEVEL_BEST, fileobj=None, mtime=None):
compresslevel=_COMPRESS_LEVEL_TRADEOFF, fileobj=None, mtime=None):
"""Constructor for the GzipFile class.

At least one of fileobj and filename must be given a
Expand DownExpand Up@@ -621,7 +621,7 @@ def _rewind(self):
self._new_member = True


def compress(data, compresslevel=_COMPRESS_LEVEL_BEST, *, mtime=0):
def compress(data, compresslevel=_COMPRESS_LEVEL_TRADEOFF, *, mtime=0):
"""Compress data in one shot and return the compressed string.

compresslevel sets the compression level in range of 0-9.
Expand Down
4 changes: 2 additions & 2 deletionsLib/tarfile.py
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Expand Up@@ -1927,7 +1927,7 @@ def not_compressed(comptype):
if "preset" in kwargs and comptype not in ("xz",):
raise ValueError("preset is only valid for w|xz mode")

compresslevel = kwargs.pop("compresslevel",9)
compresslevel = kwargs.pop("compresslevel",6)
preset = kwargs.pop("preset", None)
stream = _Stream(name, filemode, comptype, fileobj, bufsize,
compresslevel, preset)
Expand All@@ -1953,7 +1953,7 @@ def taropen(cls, name, mode="r", fileobj=None, **kwargs):
return cls(name, mode, fileobj, **kwargs)

@classmethod
def gzopen(cls, name, mode="r", fileobj=None, compresslevel=9, **kwargs):
def gzopen(cls, name, mode="r", fileobj=None, compresslevel=6, **kwargs):
"""Open gzip compressed tar archive name for reading or writing.
Appending is not allowed.
"""
Expand Down
2 changes: 1 addition & 1 deletionLib/test/test_gzip.py
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Expand Up@@ -353,7 +353,7 @@ def test_mtime(self):
def test_metadata(self):
mtime = 123456789

with gzip.GzipFile(self.filename, 'w', mtime = mtime) as fWrite:
with gzip.GzipFile(self.filename, 'w', mtime = mtime, compresslevel = 9) as fWrite:
fWrite.write(data1)

with open(self.filename, 'rb') as fRead:
Expand Down
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@@ -0,0 +1,3 @@
Adjust default compression level to 6 (down from 9) in gzip and tarfile.
It is the default level used by most compression tools and a better
tradeoff between speed and performance.
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