mirror of
https://github.com/python/cpython.git
synced 2024-12-02 22:35:26 +08:00
203 lines
6.8 KiB
ReStructuredText
203 lines
6.8 KiB
ReStructuredText
:mod:`bz2` --- Support for :program:`bzip2` compression
|
|
=======================================================
|
|
|
|
.. module:: bz2
|
|
:synopsis: Interfaces for bzip2 compression and decompression.
|
|
.. moduleauthor:: Gustavo Niemeyer <niemeyer@conectiva.com>
|
|
.. moduleauthor:: Nadeem Vawda <nadeem.vawda@gmail.com>
|
|
.. sectionauthor:: Gustavo Niemeyer <niemeyer@conectiva.com>
|
|
.. sectionauthor:: Nadeem Vawda <nadeem.vawda@gmail.com>
|
|
|
|
|
|
This module provides a comprehensive interface for compressing and
|
|
decompressing data using the bzip2 compression algorithm.
|
|
|
|
The :mod:`bz2` module contains:
|
|
|
|
* The :func:`.open` function and :class:`BZ2File` class for reading and
|
|
writing compressed files.
|
|
* The :class:`BZ2Compressor` and :class:`BZ2Decompressor` classes for
|
|
incremental (de)compression.
|
|
* The :func:`compress` and :func:`decompress` functions for one-shot
|
|
(de)compression.
|
|
|
|
All of the classes in this module may safely be accessed from multiple threads.
|
|
|
|
|
|
(De)compression of files
|
|
------------------------
|
|
|
|
.. function:: open(filename, mode='r', compresslevel=9, encoding=None, errors=None, newline=None)
|
|
|
|
Open a bzip2-compressed file in binary or text mode, returning a :term:`file
|
|
object`.
|
|
|
|
As with the constructor for :class:`BZ2File`, 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'``, ``'w'``, ``'wb'``,
|
|
``'a'``, or ``'ab'`` for binary mode, or ``'rt'``, ``'wt'``, or ``'at'`` for
|
|
text mode. The default is ``'rb'``.
|
|
|
|
The *compresslevel* argument is an integer from 1 to 9, as for the
|
|
:class:`BZ2File` constructor.
|
|
|
|
For binary mode, this function is equivalent to the :class:`BZ2File`
|
|
constructor: ``BZ2File(filename, mode, compresslevel=compresslevel)``. In
|
|
this case, the *encoding*, *errors* and *newline* arguments must not be
|
|
provided.
|
|
|
|
For text mode, a :class:`BZ2File` object is created, and wrapped in an
|
|
:class:`io.TextIOWrapper` instance with the specified encoding, error
|
|
handling behavior, and line ending(s).
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
|
|
.. class:: BZ2File(filename, mode='r', buffering=None, compresslevel=9)
|
|
|
|
Open a bzip2-compressed file in binary mode.
|
|
|
|
If *filename* is a :class:`str` or :class:`bytes` object, open the named file
|
|
directly. Otherwise, *filename* should be a :term:`file object`, which will
|
|
be used to read or write the compressed data.
|
|
|
|
The *mode* argument can be either ``'r'`` for reading (default), ``'w'`` for
|
|
overwriting, or ``'a'`` for appending. These can equivalently be given as
|
|
``'rb'``, ``'wb'``, and ``'ab'`` respectively.
|
|
|
|
If *filename* is a file object (rather than an actual file name), a mode of
|
|
``'w'`` does not truncate the file, and is instead equivalent to ``'a'``.
|
|
|
|
The *buffering* argument is ignored. Its use is deprecated.
|
|
|
|
If *mode* is ``'w'`` or ``'a'``, *compresslevel* can be a number between
|
|
``1`` and ``9`` specifying the level of compression: ``1`` produces the
|
|
least compression, and ``9`` (default) produces the most compression.
|
|
|
|
If *mode* is ``'r'``, the input file may be the concatenation of multiple
|
|
compressed streams.
|
|
|
|
:class:`BZ2File` provides all of the members specified by the
|
|
:class:`io.BufferedIOBase`, except for :meth:`detach` and :meth:`truncate`.
|
|
Iteration and the :keyword:`with` statement are supported.
|
|
|
|
:class:`BZ2File` also provides the following method:
|
|
|
|
.. method:: peek([n])
|
|
|
|
Return buffered data without advancing the file position. At least one
|
|
byte of data will be returned (unless at EOF). The exact number of bytes
|
|
returned is unspecified.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
.. versionchanged:: 3.1
|
|
Support for the :keyword:`with` statement was added.
|
|
|
|
.. versionchanged:: 3.3
|
|
The :meth:`fileno`, :meth:`readable`, :meth:`seekable`, :meth:`writable`,
|
|
:meth:`read1` and :meth:`readinto` methods were added.
|
|
|
|
.. versionchanged:: 3.3
|
|
Support was added for *filename* being a :term:`file object` instead of an
|
|
actual filename.
|
|
|
|
.. versionchanged:: 3.3
|
|
The ``'a'`` (append) mode was added, along with support for reading
|
|
multi-stream files.
|
|
|
|
|
|
Incremental (de)compression
|
|
---------------------------
|
|
|
|
.. class:: BZ2Compressor(compresslevel=9)
|
|
|
|
Create a new compressor object. This object may be used to compress data
|
|
incrementally. For one-shot compression, use the :func:`compress` function
|
|
instead.
|
|
|
|
*compresslevel*, if given, must be a number between ``1`` and ``9``. The
|
|
default is ``9``.
|
|
|
|
.. method:: compress(data)
|
|
|
|
Provide data to the compressor object. Returns a chunk of compressed data
|
|
if possible, or an empty byte string otherwise.
|
|
|
|
When you have finished providing data to the compressor, call the
|
|
:meth:`flush` method to finish the compression process.
|
|
|
|
|
|
.. method:: flush()
|
|
|
|
Finish the compression process. Returns the compressed data left in
|
|
internal buffers.
|
|
|
|
The compressor object may not be used after this method has been called.
|
|
|
|
|
|
.. class:: BZ2Decompressor()
|
|
|
|
Create a new decompressor object. This object may be used to decompress data
|
|
incrementally. For one-shot compression, use the :func:`decompress` function
|
|
instead.
|
|
|
|
.. note::
|
|
This class does not transparently handle inputs containing multiple
|
|
compressed streams, unlike :func:`decompress` and :class:`BZ2File`. If
|
|
you need to decompress a multi-stream input with :class:`BZ2Decompressor`,
|
|
you must use a new decompressor for each stream.
|
|
|
|
.. method:: decompress(data)
|
|
|
|
Provide data to the decompressor object. Returns a chunk of decompressed
|
|
data if possible, or an empty byte string otherwise.
|
|
|
|
Attempting to decompress data after the end of the current stream is
|
|
reached raises an :exc:`EOFError`. If any data is found after the end of
|
|
the stream, it is ignored and saved in the :attr:`unused_data` attribute.
|
|
|
|
|
|
.. attribute:: eof
|
|
|
|
True if the end-of-stream marker has been reached.
|
|
|
|
.. versionadded:: 3.3
|
|
|
|
|
|
.. attribute:: unused_data
|
|
|
|
Data found after the end of the compressed stream.
|
|
|
|
If this attribute is accessed before the end of the stream has been
|
|
reached, its value will be ``b''``.
|
|
|
|
|
|
One-shot (de)compression
|
|
------------------------
|
|
|
|
.. function:: compress(data, compresslevel=9)
|
|
|
|
Compress *data*.
|
|
|
|
*compresslevel*, if given, must be a number between ``1`` and ``9``. The
|
|
default is ``9``.
|
|
|
|
For incremental compression, use a :class:`BZ2Compressor` instead.
|
|
|
|
|
|
.. function:: decompress(data)
|
|
|
|
Decompress *data*.
|
|
|
|
If *data* is the concatenation of multiple compressed streams, decompress
|
|
all of the streams.
|
|
|
|
For incremental decompression, use a :class:`BZ2Decompressor` instead.
|
|
|
|
.. versionchanged:: 3.3
|
|
Support for multi-stream inputs was added.
|
|
|