bz2— Compression compatible with bzip2
New in version 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 summary of the features offered by the bz2 module:
BZ2Fileclass implements a complete file interface, including
BZ2Fileclass implements emulated
BZ2Fileclass implements universal newline support;
BZ2Fileclass offers an optimized line iteration using the readahead algorithm borrowed from file objects;
Handling of multi-stream bzip2 files is not supported. Modules such as bz2file let you overcome this.
Handling of compressed files is offered by the
BZ2File(filename[, mode[, buffering[, compresslevel]]])
Open a bz2 file. Mode can be either
'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,
unbuffered, and larger numbers specify the buffer size; the default is
0. If compresslevel is given, it must be a number between
9; the default is
9. Add a
'U' to mode to open the file for input
in universal newlines mode. Any line ending in the input file will be
seen as a
'\n' in Python. Also, a file so opened gains the attribute
newlines; the value for this attribute is one of
None (no newline
'\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
Changed in version 2.7: Support for the
with statement was added.
This class does not support input files containing multiple streams (such
as those produced by the pbzip2 tool). When reading such an
input file, only the first stream will be accessible. If you require
support for multi-stream files, consider using the third-party
bz2file module (available from
PyPI). This module provides a
backport of Python 3.3’s
BZ2File class, which does support
Close the file. Sets data attribute
closed to true. A closed file
cannot be used for further I/O operations.
close() may be called
more than once without error.
Read at most size uncompressed bytes, returned as a string. If the size argument is negative or omitted, read until EOF is reached.
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.
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.
For backward compatibility.
BZ2File objects now include the
performance optimizations previously implemented in the
Deprecated since version 2.3: This exists only for compatibility with the method by this name on
file objects, which is deprecated. Use
for line in file
Move to new file position. Argument offset is a byte count. Optional
argument whence defaults to
0 (offset from start
of file; offset should be
>= 0); other values are
1 (move relative to current position; offset can be positive 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.
Return the current file position, an integer (may be a long integer).
Write string data to file. Note that due to buffering,
be needed before the file on disk reflects the data written.
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.
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
compress() function instead. The compresslevel parameter, if given,
must be a number between
9; the default is
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
flush() method to finish the compression process,
and return what is left in internal buffers.
Finish the compression process and return what is left in internal buffers. You must not use the compressor object after calling this method.
EOFErrorwill be raised. If any data was found after the end of stream, it’ll be ignored and saved in
BZ2Compressorinstead. The compresslevel parameter, if given, must be a number between
9; the default is