1 :mod:`bz2` --- Support for :program:`bzip2` compression 2 ======================================================= 3 4 .. module:: bz2 5 :synopsis: Interfaces for bzip2 compression and decompression. 6 7 .. moduleauthor:: Gustavo Niemeyer <niemeyer (a] conectiva.com> 8 .. moduleauthor:: Nadeem Vawda <nadeem.vawda (a] gmail.com> 9 .. sectionauthor:: Gustavo Niemeyer <niemeyer (a] conectiva.com> 10 .. sectionauthor:: Nadeem Vawda <nadeem.vawda (a] gmail.com> 11 12 **Source code:** :source:`Lib/bz2.py` 13 14 -------------- 15 16 This module provides a comprehensive interface for compressing and 17 decompressing data using the bzip2 compression algorithm. 18 19 The :mod:`bz2` module contains: 20 21 * The :func:`.open` function and :class:`BZ2File` class for reading and 22 writing compressed files. 23 * The :class:`BZ2Compressor` and :class:`BZ2Decompressor` classes for 24 incremental (de)compression. 25 * The :func:`compress` and :func:`decompress` functions for one-shot 26 (de)compression. 27 28 All of the classes in this module may safely be accessed from multiple threads. 29 30 31 (De)compression of files 32 ------------------------ 33 34 .. function:: open(filename, mode='r', compresslevel=9, encoding=None, errors=None, newline=None) 35 36 Open a bzip2-compressed file in binary or text mode, returning a :term:`file 37 object`. 38 39 As with the constructor for :class:`BZ2File`, the *filename* argument can be 40 an actual filename (a :class:`str` or :class:`bytes` object), or an existing 41 file object to read from or write to. 42 43 The *mode* argument can be any of ``'r'``, ``'rb'``, ``'w'``, ``'wb'``, 44 ``'x'``, ``'xb'``, ``'a'`` or ``'ab'`` for binary mode, or ``'rt'``, 45 ``'wt'``, ``'xt'``, or ``'at'`` for text mode. The default is ``'rb'``. 46 47 The *compresslevel* argument is an integer from 1 to 9, as for the 48 :class:`BZ2File` constructor. 49 50 For binary mode, this function is equivalent to the :class:`BZ2File` 51 constructor: ``BZ2File(filename, mode, compresslevel=compresslevel)``. In 52 this case, the *encoding*, *errors* and *newline* arguments must not be 53 provided. 54 55 For text mode, a :class:`BZ2File` object is created, and wrapped in an 56 :class:`io.TextIOWrapper` instance with the specified encoding, error 57 handling behavior, and line ending(s). 58 59 .. versionadded:: 3.3 60 61 .. versionchanged:: 3.4 62 The ``'x'`` (exclusive creation) mode was added. 63 64 .. versionchanged:: 3.6 65 Accepts a :term:`path-like object`. 66 67 68 .. class:: BZ2File(filename, mode='r', buffering=None, compresslevel=9) 69 70 Open a bzip2-compressed file in binary mode. 71 72 If *filename* is a :class:`str` or :class:`bytes` object, open the named file 73 directly. Otherwise, *filename* should be a :term:`file object`, which will 74 be used to read or write the compressed data. 75 76 The *mode* argument can be either ``'r'`` for reading (default), ``'w'`` for 77 overwriting, ``'x'`` for exclusive creation, or ``'a'`` for appending. These 78 can equivalently be given as ``'rb'``, ``'wb'``, ``'xb'`` and ``'ab'`` 79 respectively. 80 81 If *filename* is a file object (rather than an actual file name), a mode of 82 ``'w'`` does not truncate the file, and is instead equivalent to ``'a'``. 83 84 The *buffering* argument is ignored. Its use is deprecated. 85 86 If *mode* is ``'w'`` or ``'a'``, *compresslevel* can be a number between 87 ``1`` and ``9`` specifying the level of compression: ``1`` produces the 88 least compression, and ``9`` (default) produces the most compression. 89 90 If *mode* is ``'r'``, the input file may be the concatenation of multiple 91 compressed streams. 92 93 :class:`BZ2File` provides all of the members specified by the 94 :class:`io.BufferedIOBase`, except for :meth:`detach` and :meth:`truncate`. 95 Iteration and the :keyword:`with` statement are supported. 96 97 :class:`BZ2File` also provides the following method: 98 99 .. method:: peek([n]) 100 101 Return buffered data without advancing the file position. At least one 102 byte of data will be returned (unless at EOF). The exact number of bytes 103 returned is unspecified. 104 105 .. note:: While calling :meth:`peek` does not change the file position of 106 the :class:`BZ2File`, it may change the position of the underlying file 107 object (e.g. if the :class:`BZ2File` was constructed by passing a file 108 object for *filename*). 109 110 .. versionadded:: 3.3 111 112 .. versionchanged:: 3.1 113 Support for the :keyword:`with` statement was added. 114 115 .. versionchanged:: 3.3 116 The :meth:`fileno`, :meth:`readable`, :meth:`seekable`, :meth:`writable`, 117 :meth:`read1` and :meth:`readinto` methods were added. 118 119 .. versionchanged:: 3.3 120 Support was added for *filename* being a :term:`file object` instead of an 121 actual filename. 122 123 .. versionchanged:: 3.3 124 The ``'a'`` (append) mode was added, along with support for reading 125 multi-stream files. 126 127 .. versionchanged:: 3.4 128 The ``'x'`` (exclusive creation) mode was added. 129 130 .. versionchanged:: 3.5 131 The :meth:`~io.BufferedIOBase.read` method now accepts an argument of 132 ``None``. 133 134 .. versionchanged:: 3.6 135 Accepts a :term:`path-like object`. 136 137 138 Incremental (de)compression 139 --------------------------- 140 141 .. class:: BZ2Compressor(compresslevel=9) 142 143 Create a new compressor object. This object may be used to compress data 144 incrementally. For one-shot compression, use the :func:`compress` function 145 instead. 146 147 *compresslevel*, if given, must be a number between ``1`` and ``9``. The 148 default is ``9``. 149 150 .. method:: compress(data) 151 152 Provide data to the compressor object. Returns a chunk of compressed data 153 if possible, or an empty byte string otherwise. 154 155 When you have finished providing data to the compressor, call the 156 :meth:`flush` method to finish the compression process. 157 158 159 .. method:: flush() 160 161 Finish the compression process. Returns the compressed data left in 162 internal buffers. 163 164 The compressor object may not be used after this method has been called. 165 166 167 .. class:: BZ2Decompressor() 168 169 Create a new decompressor object. This object may be used to decompress data 170 incrementally. For one-shot compression, use the :func:`decompress` function 171 instead. 172 173 .. note:: 174 This class does not transparently handle inputs containing multiple 175 compressed streams, unlike :func:`decompress` and :class:`BZ2File`. If 176 you need to decompress a multi-stream input with :class:`BZ2Decompressor`, 177 you must use a new decompressor for each stream. 178 179 .. method:: decompress(data, max_length=-1) 180 181 Decompress *data* (a :term:`bytes-like object`), returning 182 uncompressed data as bytes. Some of *data* may be buffered 183 internally, for use in later calls to :meth:`decompress`. The 184 returned data should be concatenated with the output of any 185 previous calls to :meth:`decompress`. 186 187 If *max_length* is nonnegative, returns at most *max_length* 188 bytes of decompressed data. If this limit is reached and further 189 output can be produced, the :attr:`~.needs_input` attribute will 190 be set to ``False``. In this case, the next call to 191 :meth:`~.decompress` may provide *data* as ``b''`` to obtain 192 more of the output. 193 194 If all of the input data was decompressed and returned (either 195 because this was less than *max_length* bytes, or because 196 *max_length* was negative), the :attr:`~.needs_input` attribute 197 will be set to ``True``. 198 199 Attempting to decompress data after the end of stream is reached 200 raises an `EOFError`. Any data found after the end of the 201 stream is ignored and saved in the :attr:`~.unused_data` attribute. 202 203 .. versionchanged:: 3.5 204 Added the *max_length* parameter. 205 206 .. attribute:: eof 207 208 ``True`` if the end-of-stream marker has been reached. 209 210 .. versionadded:: 3.3 211 212 213 .. attribute:: unused_data 214 215 Data found after the end of the compressed stream. 216 217 If this attribute is accessed before the end of the stream has been 218 reached, its value will be ``b''``. 219 220 .. attribute:: needs_input 221 222 ``False`` if the :meth:`.decompress` method can provide more 223 decompressed data before requiring new uncompressed input. 224 225 .. versionadded:: 3.5 226 227 228 One-shot (de)compression 229 ------------------------ 230 231 .. function:: compress(data, compresslevel=9) 232 233 Compress *data*. 234 235 *compresslevel*, if given, must be a number between ``1`` and ``9``. The 236 default is ``9``. 237 238 For incremental compression, use a :class:`BZ2Compressor` instead. 239 240 241 .. function:: decompress(data) 242 243 Decompress *data*. 244 245 If *data* is the concatenation of multiple compressed streams, decompress 246 all of the streams. 247 248 For incremental decompression, use a :class:`BZ2Decompressor` instead. 249 250 .. versionchanged:: 3.3 251 Support for multi-stream inputs was added. 252 253
