2007-08-15 11:28:22 -03:00
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:mod:`gzip` --- Support for :program:`gzip` files
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=================================================
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.. module:: gzip
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:synopsis: Interfaces for gzip compression and decompression using file objects.
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The data compression provided by the ``zlib`` module is compatible with that
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used by the GNU compression program :program:`gzip`. Accordingly, the
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:mod:`gzip` module provides the :class:`GzipFile` class to read and write
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:program:`gzip`\ -format files, automatically compressing or decompressing the
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data so it looks like an ordinary file object. Note that additional file
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formats which can be decompressed by the :program:`gzip` and :program:`gunzip`
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programs, such as those produced by :program:`compress` and :program:`pack`,
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are not supported by this module.
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Merged revisions 58817-58861 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk
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r58822 | brett.cannon | 2007-11-02 23:47:02 -0700 (Fri, 02 Nov 2007) | 2 lines
Add a missing quotation mark.
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r58840 | skip.montanaro | 2007-11-04 07:56:52 -0800 (Sun, 04 Nov 2007) | 2 lines
Note change to get_dialect semantics in 2.5. Will backport to 2.5.
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r58844 | georg.brandl | 2007-11-04 09:43:49 -0800 (Sun, 04 Nov 2007) | 2 lines
Fix syntax for versionchanged markup.
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r58850 | gregory.p.smith | 2007-11-04 18:32:26 -0800 (Sun, 04 Nov 2007) | 9 lines
Fixes bug 477182 on pybsddb.sf.net. DB objects now load the flags and
pay attention to them when opening an existing database. This means
that d[] behaves properly even on databases previously created with DB_DUP
or DB_DUPSORT flags to allow duplicate keys.
http://sourceforge.net/tracker/index.php?func=detail&aid=477182&group_id=13900&atid=113900
Do not backport, this bugfix could be considered an API change.
........
r58851 | gregory.p.smith | 2007-11-04 18:56:31 -0800 (Sun, 04 Nov 2007) | 3 lines
Add the bsddb.db.DBEnv.lock_id_free method.
Improve test_lock's tempdir creation and cleanup.
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r58852 | gregory.p.smith | 2007-11-05 01:06:28 -0800 (Mon, 05 Nov 2007) | 3 lines
* db->get_types is only available in BerkeleyDB >= 4.2
* get compiling with older versions of python again for a stand alone release.
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r58853 | gregory.p.smith | 2007-11-05 01:07:40 -0800 (Mon, 05 Nov 2007) | 2 lines
* db->get_flags is only available in BerkeleyDB >= 4.2
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r58854 | mark.summerfield | 2007-11-05 01:22:48 -0800 (Mon, 05 Nov 2007) | 3 lines
Added cross-references between the various archive file formats.
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r58857 | mark.summerfield | 2007-11-05 06:38:50 -0800 (Mon, 05 Nov 2007) | 5 lines
Clarified the fact that you can have comments for individual archive
members even though comments to the archive itself aren't currently
supported.
........
2007-11-05 15:43:04 -04:00
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For other archive formats, see the :mod:`bz2`, :mod:`zipfile`, and
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:mod:`tarfile` modules.
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2007-08-15 11:28:22 -03:00
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The module defines the following items:
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.. class:: GzipFile([filename[, mode[, compresslevel[, fileobj]]]])
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Constructor for the :class:`GzipFile` class, which simulates most of the methods
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of a file object, with the exception of the :meth:`readinto` and
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:meth:`truncate` methods. At least one of *fileobj* and *filename* must be
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given a non-trivial value.
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The new class instance is based on *fileobj*, which can be a regular file, a
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:class:`StringIO` object, or any other object which simulates a file. It
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defaults to ``None``, in which case *filename* is opened to provide a file
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object.
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When *fileobj* is not ``None``, the *filename* argument is only used to be
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included in the :program:`gzip` file header, which may includes the original
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filename of the uncompressed file. It defaults to the filename of *fileobj*, if
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discernible; otherwise, it defaults to the empty string, and in this case the
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original filename is not included in the header.
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The *mode* argument can be any of ``'r'``, ``'rb'``, ``'a'``, ``'ab'``, ``'w'``,
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or ``'wb'``, depending on whether the file will be read or written. The default
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is the mode of *fileobj* if discernible; otherwise, the default is ``'rb'``. If
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not given, the 'b' flag will be added to the mode to ensure the file is opened
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in binary mode for cross-platform portability.
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The *compresslevel* argument is an integer from ``1`` to ``9`` controlling the
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level of compression; ``1`` is fastest and produces the least compression, and
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``9`` is slowest and produces the most compression. The default is ``9``.
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Calling a :class:`GzipFile` object's :meth:`close` method does not close
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*fileobj*, since you might wish to append more material after the compressed
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data. This also allows you to pass a :class:`StringIO` object opened for
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writing as *fileobj*, and retrieve the resulting memory buffer using the
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:class:`StringIO` object's :meth:`getvalue` method.
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.. function:: open(filename[, mode[, compresslevel]])
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This is a shorthand for ``GzipFile(filename,`` ``mode,`` ``compresslevel)``.
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The *filename* argument is required; *mode* defaults to ``'rb'`` and
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*compresslevel* defaults to ``9``.
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.. seealso::
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Module :mod:`zlib`
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The basic data compression module needed to support the :program:`gzip` file
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format.
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