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:
- The
open()
function andBZ2File
class for reading and writing compressed files. - The
BZ2Compressor
andBZ2Decompressor
classes for incremental (de)compression. - The
compress()
anddecompress()
functions for one-shot (de)compression.
All of the classes in this module may safely be accessed from multiple threads.
13.3.1. (De)compression of files
-
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 (astr
orbytes
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 anio.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.
-
class bz2.BZ2File(filename, mode='r', buffering=None, compresslevel=9)
-
Open a bzip2-compressed file in binary mode.
If filename is a
str
orbytes
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 between1
and9
specifying the level of compression:1
produces the least compression, and9
(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 theio.BufferedIOBase
, except fordetach()
andtruncate()
. Iteration and thewith
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 theBZ2File
, it may change the position of the underlying file object (e.g. if theBZ2File
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()
andreadinto()
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 ofNone
.Changed in version 3.6: Accepts a path-like object.
-
13.3.2. Incremental (de)compression
-
class 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
and9
. The default is9
.-
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.
-
-
class 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()
andBZ2File
. If you need to decompress a multi-stream input withBZ2Decompressor
, 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 todecompress()
.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 toFalse
. In this case, the next call todecompress()
may provide data asb''
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 toTrue
.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 theunused_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 thedecompress()
method can provide more decompressed data before requiring new uncompressed input.New in version 3.5.
-
13.3.3. One-shot (de)compression
-
bz2.compress(data, compresslevel=9)
-
Compress data.
compresslevel, if given, must be a number between
1
and9
. The default is9
.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.
© 2001–2020 Python Software Foundation
Licensed under the PSF License.
https://docs.python.org/3.6/library/bz2.html