mirror of https://github.com/python/cpython
192 lines
6.9 KiB
ReStructuredText
192 lines
6.9 KiB
ReStructuredText
|
|
:mod:`bz2` --- Compression compatible with :program:`bzip2`
|
|
===========================================================
|
|
|
|
.. module:: bz2
|
|
:synopsis: Interface to compression and decompression routines compatible with bzip2.
|
|
.. moduleauthor:: Gustavo Niemeyer <niemeyer@conectiva.com>
|
|
.. sectionauthor:: Gustavo Niemeyer <niemeyer@conectiva.com>
|
|
|
|
|
|
.. versionadded:: 2.3
|
|
|
|
This module provides a comprehensive interface for the bz2 compression library.
|
|
It implements a complete file interface, one-shot (de)compression functions, and
|
|
types for sequential (de)compression.
|
|
|
|
Here is a resume of the features offered by the bz2 module:
|
|
|
|
* :class:`BZ2File` class implements a complete file interface, including
|
|
:meth:`readline`, :meth:`readlines`, :meth:`writelines`, :meth:`seek`, etc;
|
|
|
|
* :class:`BZ2File` class implements emulated :meth:`seek` support;
|
|
|
|
* :class:`BZ2File` class implements universal newline support;
|
|
|
|
* :class:`BZ2File` class offers an optimized line iteration using the readahead
|
|
algorithm borrowed from file objects;
|
|
|
|
* Sequential (de)compression supported by :class:`BZ2Compressor` and
|
|
:class:`BZ2Decompressor` classes;
|
|
|
|
* One-shot (de)compression supported by :func:`compress` and :func:`decompress`
|
|
functions;
|
|
|
|
* Thread safety uses individual locking mechanism;
|
|
|
|
* Complete inline documentation;
|
|
|
|
|
|
(De)compression of files
|
|
------------------------
|
|
|
|
Handling of compressed files is offered by the :class:`BZ2File` class.
|
|
|
|
|
|
.. class:: BZ2File(filename[, mode[, buffering[, compresslevel]]])
|
|
|
|
Open a bz2 file. Mode can be either ``'r'`` or ``'w'``, for reading (default)
|
|
or writing. When opened for writing, the file will be created if it doesn't
|
|
exist, and truncated otherwise. If *buffering* is given, ``0`` means unbuffered,
|
|
and larger numbers specify the buffer size; the default is ``0``. If
|
|
*compresslevel* is given, it must be a number between ``1`` and ``9``; the
|
|
default is ``9``. Add a ``'U'`` to mode to open the file for input with
|
|
universal newline support. Any line ending in the input file will be seen as a
|
|
``'\n'`` in Python. Also, a file so opened gains the attribute
|
|
:attr:`newlines`; the value for this attribute is one of ``None`` (no newline
|
|
read yet), ``'\r'``, ``'\n'``, ``'\r\n'`` or a tuple containing all the newline
|
|
types seen. Universal newlines are available only when reading. Instances
|
|
support iteration in the same way as normal :class:`file` instances.
|
|
|
|
|
|
.. method:: BZ2File.close()
|
|
|
|
Close the file. Sets data attribute :attr:`closed` to true. A closed file cannot
|
|
be used for further I/O operations. :meth:`close` may be called more than once
|
|
without error.
|
|
|
|
|
|
.. method:: BZ2File.read([size])
|
|
|
|
Read at most *size* uncompressed bytes, returned as a string. If the *size*
|
|
argument is negative or omitted, read until EOF is reached.
|
|
|
|
|
|
.. method:: BZ2File.readline([size])
|
|
|
|
Return the next line from the file, as a string, retaining newline. A
|
|
non-negative *size* argument limits the maximum number of bytes to return (an
|
|
incomplete line may be returned then). Return an empty string at EOF.
|
|
|
|
|
|
.. method:: BZ2File.readlines([size])
|
|
|
|
Return a list of lines read. The optional *size* argument, if given, is an
|
|
approximate bound on the total number of bytes in the lines returned.
|
|
|
|
|
|
.. method:: BZ2File.xreadlines()
|
|
|
|
For backward compatibility. :class:`BZ2File` objects now include the performance
|
|
optimizations previously implemented in the :mod:`xreadlines` module.
|
|
|
|
.. deprecated:: 2.3
|
|
This exists only for compatibility with the method by this name on :class:`file`
|
|
objects, which is deprecated. Use ``for line in file`` instead.
|
|
|
|
|
|
.. method:: BZ2File.seek(offset[, whence])
|
|
|
|
Move to new file position. Argument *offset* is a byte count. Optional argument
|
|
*whence* defaults to ``os.SEEK_SET`` or ``0`` (offset from start of file; offset
|
|
should be ``>= 0``); other values are ``os.SEEK_CUR`` or ``1`` (move relative to
|
|
current position; offset can be positive or negative), and ``os.SEEK_END`` or
|
|
``2`` (move relative to end of file; offset is usually negative, although many
|
|
platforms allow seeking beyond the end of a file).
|
|
|
|
Note that seeking of bz2 files is emulated, and depending on the parameters the
|
|
operation may be extremely slow.
|
|
|
|
|
|
.. method:: BZ2File.tell()
|
|
|
|
Return the current file position, an integer (may be a long integer).
|
|
|
|
|
|
.. method:: BZ2File.write(data)
|
|
|
|
Write string *data* to file. Note that due to buffering, :meth:`close` may be
|
|
needed before the file on disk reflects the data written.
|
|
|
|
|
|
.. method:: BZ2File.writelines(sequence_of_strings)
|
|
|
|
Write the sequence of strings to the file. Note that newlines are not added. The
|
|
sequence can be any iterable object producing strings. This is equivalent to
|
|
calling write() for each string.
|
|
|
|
|
|
Sequential (de)compression
|
|
--------------------------
|
|
|
|
Sequential compression and decompression is done using the classes
|
|
:class:`BZ2Compressor` and :class:`BZ2Decompressor`.
|
|
|
|
|
|
.. class:: BZ2Compressor([compresslevel])
|
|
|
|
Create a new compressor object. This object may be used to compress data
|
|
sequentially. If you want to compress data in one shot, use the :func:`compress`
|
|
function instead. The *compresslevel* parameter, if given, must be a number
|
|
between ``1`` and ``9``; the default is ``9``.
|
|
|
|
|
|
.. method:: BZ2Compressor.compress(data)
|
|
|
|
Provide more data to the compressor object. It will return chunks of compressed
|
|
data whenever possible. When you've finished providing data to compress, call
|
|
the :meth:`flush` method to finish the compression process, and return what is
|
|
left in internal buffers.
|
|
|
|
|
|
.. method:: BZ2Compressor.flush()
|
|
|
|
Finish the compression process and return what is left in internal buffers. You
|
|
must not use the compressor object after calling this method.
|
|
|
|
|
|
.. class:: BZ2Decompressor()
|
|
|
|
Create a new decompressor object. This object may be used to decompress data
|
|
sequentially. If you want to decompress data in one shot, use the
|
|
:func:`decompress` function instead.
|
|
|
|
|
|
.. method:: BZ2Decompressor.decompress(data)
|
|
|
|
Provide more data to the decompressor object. It will return chunks of
|
|
decompressed data whenever possible. If you try to decompress data after the end
|
|
of stream is found, :exc:`EOFError` will be raised. If any data was found after
|
|
the end of stream, it'll be ignored and saved in :attr:`unused_data` attribute.
|
|
|
|
|
|
One-shot (de)compression
|
|
------------------------
|
|
|
|
One-shot compression and decompression is provided through the :func:`compress`
|
|
and :func:`decompress` functions.
|
|
|
|
|
|
.. function:: compress(data[, compresslevel])
|
|
|
|
Compress *data* in one shot. If you want to compress data sequentially, use an
|
|
instance of :class:`BZ2Compressor` instead. The *compresslevel* parameter, if
|
|
given, must be a number between ``1`` and ``9``; the default is ``9``.
|
|
|
|
|
|
.. function:: decompress(data)
|
|
|
|
Decompress *data* in one shot. If you want to decompress data sequentially, use
|
|
an instance of :class:`BZ2Decompressor` instead.
|
|
|