| :mod:`gzip` --- Support for :program:`gzip` files |
| ================================================= |
| |
| .. module:: gzip |
| :synopsis: Interfaces for gzip compression and decompression using file objects. |
| |
| 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 which is modeled |
| after Python's File Object. The :class:`GzipFile` class reads and writes |
| :program:`gzip`\ -format files, automatically compressing or decompressing the |
| data so that 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. |
| |
| For other archive formats, see the :mod:`bz2`, :mod:`zipfile`, and |
| :mod:`tarfile` modules. |
| |
| 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``. |
| |
| |
| .. _gzip-usage-examples: |
| |
| Examples of usage |
| ----------------- |
| |
| Example of how to read a compressed file:: |
| |
| import gzip |
| f = gzip.open('/home/joe/file.txt.gz', 'rb') |
| file_content = f.read() |
| f.close() |
| |
| Example of how to create a compressed GZIP file:: |
| |
| import gzip |
| content = "Lots of content here" |
| f = gzip.open('/home/joe/file.txt.gz', 'wb') |
| f.write(content) |
| f.close() |
| |
| Example of how to GZIP compress an existing file:: |
| |
| import gzip |
| f_in = open('/home/joe/file.txt', 'rb') |
| f_out = gzip.open('/home/joe/file.txt.gz', 'wb') |
| f_out.writelines(f_in) |
| f_out.close() |
| f_in.close() |
| |
| |
| .. seealso:: |
| |
| Module :mod:`zlib` |
| The basic data compression module needed to support the :program:`gzip` file |
| format. |
| |