69 lines
3.1 KiB
ReStructuredText
69 lines
3.1 KiB
ReStructuredText
|
|
:mod:`gzip` --- Support for :program:`gzip` files
|
|
=================================================
|
|
|
|
.. module:: gzip
|
|
:synopsis: Interfaces for gzip compression and decompression using file objects.
|
|
|
|
|
|
The data compression provided by the ``zlib`` module is compatible with that
|
|
used by the GNU compression program :program:`gzip`. Accordingly, the
|
|
:mod:`gzip` module provides the :class:`GzipFile` class to read and write
|
|
:program:`gzip`\ -format files, automatically compressing or decompressing the
|
|
data so it looks like an ordinary 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:
|
|
|
|
|
|
.. class:: GzipFile([filename[, mode[, compresslevel[, fileobj]]]])
|
|
|
|
Constructor for the :class:`GzipFile` class, which simulates most of the methods
|
|
of a file object, with the exception of the :meth:`readinto` and
|
|
:meth:`truncate` methods. 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, a
|
|
:class:`StringIO` 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 includes 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'``,
|
|
or ``'wb'``, depending on whether the file will be read or written. The default
|
|
is the mode of *fileobj* if discernible; otherwise, the default is ``'rb'``. If
|
|
not given, the 'b' flag will be added to the mode to ensure the file is opened
|
|
in binary mode for cross-platform portability.
|
|
|
|
The *compresslevel* argument is an integer from ``1`` to ``9`` controlling the
|
|
level of compression; ``1`` is fastest and produces the least compression, and
|
|
``9`` is slowest and produces the most compression. The default is ``9``.
|
|
|
|
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 a :class:`StringIO` object opened for
|
|
writing as *fileobj*, and retrieve the resulting memory buffer using the
|
|
:class:`StringIO` object's :meth:`getvalue` method.
|
|
|
|
|
|
.. function:: open(filename[, mode[, compresslevel]])
|
|
|
|
This is a shorthand for ``GzipFile(filename,`` ``mode,`` ``compresslevel)``.
|
|
The *filename* argument is required; *mode* defaults to ``'rb'`` and
|
|
*compresslevel* defaults to ``9``.
|
|
|
|
|
|
.. seealso::
|
|
|
|
Module :mod:`zlib`
|
|
The basic data compression module needed to support the :program:`gzip` file
|
|
format.
|
|
|