bz2 — Support for bzip2 compression¶Source code: Lib/bz2.py
This module provides a comprehensive interface for compressing and decompressing data using the bzip2 compression algorithm.
The bz2 module contains:
open() function and BZ2File class for reading and
writing compressed files.BZ2Compressor and BZ2Decompressor classes for
incremental (de)compression.compress() and decompress() functions for one-shot
(de)compression.All of the classes in this module may safely be accessed from multiple threads.
bz2.open(filename, mode='r', compresslevel=9, encoding=None, errors=None, newline=None)¶Open a bzip2-compressed file in binary or text mode, returning a file object.
As with the constructor for BZ2File, the filename argument can be
an actual filename (a str or bytes object), or an existing
file object to read from or write to.
The mode argument can be any of 'r', 'rb', 'w', 'wb',
'x', 'xb', 'a' or 'ab' for binary mode, or 'rt',
'wt', 'xt', or 'at' for text mode. The default is 'rb'.
The compresslevel argument is an integer from 1 to 9, as for the
BZ2File constructor.
For binary mode, this function is equivalent to the BZ2File
constructor: BZ2File(filename, mode, compresslevel=compresslevel). In
this case, the encoding, errors and newline arguments must not be
provided.
For text mode, a BZ2File object is created, and wrapped in an
io.TextIOWrapper instance with the specified encoding, error
handling behavior, and line ending(s).
New in version 3.3.
Changed in version 3.4: The 'x' (exclusive creation) mode was added.
Changed in version 3.6: Accepts a path-like object.
bz2.BZ2File(filename, mode='r', buffering=None, compresslevel=9)¶Open a bzip2-compressed file in binary mode.
If filename is a str or bytes object, open the named file
directly. Otherwise, filename should be a 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, 'x' for exclusive creation, or 'a' for appending. These
can equivalently be given as 'rb', 'wb', 'xb' 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.
BZ2File provides all of the members specified by the
io.BufferedIOBase, except for detach() and truncate().
Iteration and the with statement are supported.
BZ2File also provides the following 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.
Note
While calling peek() does not change the file position of
the BZ2File, it may change the position of the underlying file
object (e.g. if the BZ2File was constructed by passing a file
object for filename).
New in version 3.3.
Changed in version 3.1: Support for the with statement was added.
Changed in version 3.3: The fileno(), readable(), seekable(), writable(),
read1() and readinto() methods were added.
Changed in version 3.3: Support was added for filename being a file object instead of an actual filename.
Changed in version 3.3: The 'a' (append) mode was added, along with support for reading
multi-stream files.
Changed in version 3.4: The 'x' (exclusive creation) mode was added.
Changed in version 3.5: The read() method now accepts an argument of
None.
Changed in version 3.6: Accepts a path-like object.
bz2.BZ2Compressor(compresslevel=9)¶Create a new compressor object. This object may be used to compress data
incrementally. For one-shot compression, use the compress() function
instead.
compresslevel, if given, must be a number between 1 and 9. The
default is 9.
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
flush() method to finish the compression process.
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.
bz2.BZ2Decompressor¶Create a new decompressor object. This object may be used to decompress data
incrementally. For one-shot compression, use the decompress() function
instead.
Note
This class does not transparently handle inputs containing multiple
compressed streams, unlike decompress() and BZ2File. If
you need to decompress a multi-stream input with BZ2Decompressor,
you must use a new decompressor for each stream.
decompress(data, max_length=-1)¶Decompress data (a bytes-like object), returning
uncompressed data as bytes. Some of data may be buffered
internally, for use in later calls to decompress(). The
returned data should be concatenated with the output of any
previous calls to decompress().
If max_length is nonnegative, returns at most max_length
bytes of decompressed data. If this limit is reached and further
output can be produced, the needs_input attribute will
be set to False. In this case, the next call to
decompress() may provide data as b'' to obtain
more of the output.
If all of the input data was decompressed and returned (either
because this was less than max_length bytes, or because
max_length was negative), the needs_input attribute
will be set to True.
Attempting to decompress data after the end of stream is reached
raises an EOFError. Any data found after the end of the
stream is ignored and saved in the unused_data attribute.
Changed in version 3.5: Added the max_length parameter.
eof¶True if the end-of-stream marker has been reached.
New in version 3.3.
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''.
needs_input¶False if the decompress() method can provide more
decompressed data before requiring new uncompressed input.
New in version 3.5.
bz2.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 BZ2Compressor instead.
bz2.decompress(data)¶Decompress data.
If data is the concatenation of multiple compressed streams, decompress all of the streams.
For incremental decompression, use a BZ2Decompressor instead.
Changed in version 3.3: Support for multi-stream inputs was added.