249 lines
8.7 KiB
ReStructuredText
249 lines
8.7 KiB
ReStructuredText
:mod:`gzip` --- Support for :program:`gzip` files
|
|
=================================================
|
|
|
|
.. module:: gzip
|
|
:synopsis: Interfaces for gzip compression and decompression using file objects.
|
|
|
|
**Source code:** :source:`Lib/gzip.py`
|
|
|
|
--------------
|
|
|
|
This module provides a simple interface to compress and decompress files just
|
|
like the GNU programs :program:`gzip` and :program:`gunzip` would.
|
|
|
|
The data compression is provided by the :mod:`zlib` module.
|
|
|
|
The :mod:`gzip` module provides the :class:`GzipFile` class, as well as the
|
|
:func:`.open`, :func:`compress` and :func:`decompress` convenience functions.
|
|
The :class:`GzipFile` class reads and writes :program:`gzip`\ -format files,
|
|
automatically compressing or decompressing the data so that it looks like an
|
|
ordinary :term:`file object`.
|
|
|
|
Note that additional file formats which can be decompressed by the
|
|
:program:`gzip` and :program:`gunzip` programs, such as those produced by
|
|
:program:`compress` and :program:`pack`, are not supported by this module.
|
|
|
|
The module defines the following items:
|
|
|
|
|
|
.. function:: open(filename, mode='rb', compresslevel=9, encoding=None, errors=None, newline=None)
|
|
|
|
Open a gzip-compressed file in binary or text mode, returning a :term:`file
|
|
object`.
|
|
|
|
The *filename* argument can be an actual filename (a :class:`str` or
|
|
:class:`bytes` object), or an existing file object to read from or write to.
|
|
|
|
The *mode* argument can be any of ``'r'``, ``'rb'``, ``'a'``, ``'ab'``,
|
|
``'w'``, ``'wb'``, ``'x'`` or ``'xb'`` for binary mode, or ``'rt'``,
|
|
``'at'``, ``'wt'``, or ``'xt'`` for text mode. The default is ``'rb'``.
|
|
|
|
The *compresslevel* argument is an integer from 0 to 9, as for the
|
|
:class:`GzipFile` constructor.
|
|
|
|
For binary mode, this function is equivalent to the :class:`GzipFile`
|
|
constructor: ``GzipFile(filename, mode, compresslevel)``. In this case, the
|
|
*encoding*, *errors* and *newline* arguments must not be provided.
|
|
|
|
For text mode, a :class:`GzipFile` object is created, and wrapped in an
|
|
:class:`io.TextIOWrapper` instance with the specified encoding, error
|
|
handling behavior, and line ending(s).
|
|
|
|
.. versionchanged:: 3.3
|
|
Added support for *filename* being a file object, support for text mode,
|
|
and the *encoding*, *errors* and *newline* arguments.
|
|
|
|
.. versionchanged:: 3.4
|
|
Added support for the ``'x'``, ``'xb'`` and ``'xt'`` modes.
|
|
|
|
.. versionchanged:: 3.6
|
|
Accepts a :term:`path-like object`.
|
|
|
|
.. class:: GzipFile(filename=None, mode=None, compresslevel=9, 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:`truncate`
|
|
method. At least one of *fileobj* and *filename* must be given a non-trivial
|
|
value.
|
|
|
|
The new class instance is based on *fileobj*, which can be a regular file, an
|
|
:class:`io.BytesIO` object, or any other object which simulates a file. It
|
|
defaults to ``None``, in which case *filename* is opened to provide a file
|
|
object.
|
|
|
|
When *fileobj* is not ``None``, the *filename* argument is only used to be
|
|
included in the :program:`gzip` file header, which may include the original
|
|
filename of the uncompressed file. It defaults to the filename of *fileobj*, if
|
|
discernible; otherwise, it defaults to the empty string, and in this case the
|
|
original filename is not included in the header.
|
|
|
|
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'``.
|
|
|
|
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
|
|
:class:`io.TextIOWrapper`).
|
|
|
|
The *compresslevel* argument is an integer from ``0`` to ``9`` controlling
|
|
the level of compression; ``1`` is fastest and produces the least
|
|
compression, and ``9`` is slowest and produces the most compression. ``0``
|
|
is no compression. The default is ``9``.
|
|
|
|
The *mtime* argument is an optional numeric timestamp to be written to
|
|
the last modification time field in the stream when compressing. It
|
|
should only be provided in compression mode. If omitted or ``None``, the
|
|
current time is used. See the :attr:`mtime` attribute for more details.
|
|
|
|
Calling a :class:`GzipFile` object's :meth:`close` method does not close
|
|
*fileobj*, since you might wish to append more material after the compressed
|
|
data. This also allows you to pass an :class:`io.BytesIO` object opened for
|
|
writing as *fileobj*, and retrieve the resulting memory buffer using the
|
|
:class:`io.BytesIO` object's :meth:`~io.BytesIO.getvalue` method.
|
|
|
|
:class:`GzipFile` supports the :class:`io.BufferedIOBase` interface,
|
|
including iteration and the :keyword:`with` statement. Only the
|
|
:meth:`truncate` method isn't implemented.
|
|
|
|
:class:`GzipFile` also provides the following method and attribute:
|
|
|
|
.. method:: peek(n)
|
|
|
|
Read *n* uncompressed bytes without advancing the file position.
|
|
At most one single read on the compressed stream is done to satisfy
|
|
the call. The number of bytes returned may be more or less than
|
|
requested.
|
|
|
|
.. note:: While calling :meth:`peek` does not change the file position of
|
|
the :class:`GzipFile`, it may change the position of the underlying
|
|
file object (e.g. if the :class:`GzipFile` was constructed with the
|
|
*fileobj* parameter).
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
.. attribute:: mtime
|
|
|
|
When decompressing, the value of the last modification time field in
|
|
the most recently read header may be read from this attribute, as an
|
|
integer. The initial value before reading any headers is ``None``.
|
|
|
|
All :program:`gzip` compressed streams are required to contain this
|
|
timestamp field. Some programs, such as :program:`gunzip`\ , make use
|
|
of the timestamp. The format is the same as the return value of
|
|
:func:`time.time` and the :attr:`~os.stat_result.st_mtime` attribute of
|
|
the object returned by :func:`os.stat`.
|
|
|
|
.. versionchanged:: 3.1
|
|
Support for the :keyword:`with` statement was added, along with the
|
|
*mtime* constructor argument and :attr:`mtime` attribute.
|
|
|
|
.. versionchanged:: 3.2
|
|
Support for zero-padded and unseekable files was added.
|
|
|
|
.. versionchanged:: 3.3
|
|
The :meth:`io.BufferedIOBase.read1` method is now implemented.
|
|
|
|
.. versionchanged:: 3.4
|
|
Added support for the ``'x'`` and ``'xb'`` modes.
|
|
|
|
.. versionchanged:: 3.5
|
|
Added support for writing arbitrary
|
|
:term:`bytes-like objects <bytes-like object>`.
|
|
The :meth:`~io.BufferedIOBase.read` method now accepts an argument of
|
|
``None``.
|
|
|
|
.. versionchanged:: 3.6
|
|
Accepts a :term:`path-like object`.
|
|
|
|
|
|
.. function:: compress(data, compresslevel=9)
|
|
|
|
Compress the *data*, returning a :class:`bytes` object containing
|
|
the compressed data. *compresslevel* has the same meaning as in
|
|
the :class:`GzipFile` constructor above.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
.. function:: decompress(data)
|
|
|
|
Decompress the *data*, returning a :class:`bytes` object containing the
|
|
uncompressed data.
|
|
|
|
.. versionadded:: 3.2
|
|
|
|
|
|
.. _gzip-usage-examples:
|
|
|
|
Examples of usage
|
|
-----------------
|
|
|
|
Example of how to read a compressed file::
|
|
|
|
import gzip
|
|
with gzip.open('/home/joe/file.txt.gz', 'rb') as f:
|
|
file_content = f.read()
|
|
|
|
Example of how to create a compressed GZIP file::
|
|
|
|
import gzip
|
|
content = b"Lots of content here"
|
|
with gzip.open('/home/joe/file.txt.gz', 'wb') as f:
|
|
f.write(content)
|
|
|
|
Example of how to GZIP compress an existing file::
|
|
|
|
import gzip
|
|
import shutil
|
|
with open('/home/joe/file.txt', 'rb') as f_in:
|
|
with gzip.open('/home/joe/file.txt.gz', 'wb') as f_out:
|
|
shutil.copyfileobj(f_in, f_out)
|
|
|
|
Example of how to GZIP compress a binary string::
|
|
|
|
import gzip
|
|
s_in = b"Lots of content here"
|
|
s_out = gzip.compress(s_in)
|
|
|
|
.. seealso::
|
|
|
|
Module :mod:`zlib`
|
|
The basic data compression module needed to support the :program:`gzip` file
|
|
format.
|
|
|
|
Command Line Interface
|
|
----------------------
|
|
|
|
The :mod:`gzip` module provides a simple command line interface to compress or
|
|
decompress files.
|
|
|
|
Once executed the :mod:`gzip` module keeps the input file(s).
|
|
|
|
.. versionchanged:: 3.8
|
|
|
|
Add a new command line interface with a usage.
|
|
|
|
Command line options
|
|
^^^^^^^^^^^^^^^^^^^^
|
|
|
|
.. cmdoption:: file
|
|
|
|
.. code-block:: shell-session
|
|
|
|
$ python -m gzip file
|
|
|
|
If *file* is not specified, read from :attr:`sys.stdin`.
|
|
|
|
.. cmdoption:: -d, --decompress
|
|
|
|
Decompress the given file
|
|
|
|
.. code-block:: shell-session
|
|
|
|
$ python -m gzip -d file.gz
|
|
|
|
.. cmdoption:: -h, --help
|
|
|
|
Show the help message.
|
|
|