Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 1 | :mod:`bz2` --- Support for :program:`bzip2` compression |
| 2 | ======================================================= |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 3 | |
| 4 | .. module:: bz2 |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 5 | :synopsis: Interfaces for bzip2 compression and decompression. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 6 | .. moduleauthor:: Gustavo Niemeyer <niemeyer@conectiva.com> |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 7 | .. moduleauthor:: Nadeem Vawda <nadeem.vawda@gmail.com> |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 8 | .. sectionauthor:: Gustavo Niemeyer <niemeyer@conectiva.com> |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 9 | .. sectionauthor:: Nadeem Vawda <nadeem.vawda@gmail.com> |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 10 | |
| 11 | |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 12 | This module provides a comprehensive interface for compressing and |
| 13 | decompressing data using the bzip2 compression algorithm. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 14 | |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 15 | The :mod:`bz2` module contains: |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 16 | |
Nadeem Vawda | af518c1 | 2012-06-04 23:32:38 +0200 | [diff] [blame] | 17 | * The :func:`.open` function and :class:`BZ2File` class for reading and |
| 18 | writing compressed files. |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 19 | * The :class:`BZ2Compressor` and :class:`BZ2Decompressor` classes for |
| 20 | incremental (de)compression. |
| 21 | * The :func:`compress` and :func:`decompress` functions for one-shot |
| 22 | (de)compression. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 23 | |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 24 | All of the classes in this module may safely be accessed from multiple threads. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 25 | |
| 26 | |
| 27 | (De)compression of files |
| 28 | ------------------------ |
| 29 | |
Nadeem Vawda | af518c1 | 2012-06-04 23:32:38 +0200 | [diff] [blame] | 30 | .. function:: open(filename, mode='r', compresslevel=9, encoding=None, errors=None, newline=None) |
| 31 | |
| 32 | Open a bzip2-compressed file in binary or text mode, returning a :term:`file |
| 33 | object`. |
| 34 | |
| 35 | As with the constructor for :class:`BZ2File`, the *filename* argument can be |
| 36 | an actual filename (a :class:`str` or :class:`bytes` object), or an existing |
| 37 | file object to read from or write to. |
| 38 | |
| 39 | The *mode* argument can be any of ``'r'``, ``'rb'``, ``'w'``, ``'wb'``, |
| 40 | ``'a'``, or ``'ab'`` for binary mode, or ``'rt'``, ``'wt'``, or ``'at'`` for |
| 41 | text mode. The default is ``'rb'``. |
| 42 | |
| 43 | The *compresslevel* argument is an integer from 1 to 9, as for the |
| 44 | :class:`BZ2File` constructor. |
| 45 | |
| 46 | For binary mode, this function is equivalent to the :class:`BZ2File` |
| 47 | constructor: ``BZ2File(filename, mode, compresslevel=compresslevel)``. In |
| 48 | this case, the *encoding*, *errors* and *newline* arguments must not be |
| 49 | provided. |
| 50 | |
| 51 | For text mode, a :class:`BZ2File` object is created, and wrapped in an |
| 52 | :class:`io.TextIOWrapper` instance with the specified encoding, error |
| 53 | handling behavior, and line ending(s). |
| 54 | |
| 55 | .. versionadded:: 3.3 |
| 56 | |
| 57 | |
Nadeem Vawda | aebcdba | 2012-06-04 23:31:20 +0200 | [diff] [blame] | 58 | .. class:: BZ2File(filename, mode='r', buffering=None, compresslevel=9) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 59 | |
Nadeem Vawda | af518c1 | 2012-06-04 23:32:38 +0200 | [diff] [blame] | 60 | Open a bzip2-compressed file in binary mode. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 61 | |
Nadeem Vawda | aebcdba | 2012-06-04 23:31:20 +0200 | [diff] [blame] | 62 | If *filename* is a :class:`str` or :class:`bytes` object, open the named file |
| 63 | directly. Otherwise, *filename* should be a :term:`file object`, which will |
| 64 | be used to read or write the compressed data. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 65 | |
Nadeem Vawda | 200e00a | 2011-05-27 01:52:16 +0200 | [diff] [blame] | 66 | The *mode* argument can be either ``'r'`` for reading (default), ``'w'`` for |
Nadeem Vawda | 50cb936 | 2012-06-04 23:31:22 +0200 | [diff] [blame] | 67 | overwriting, or ``'a'`` for appending. These can equivalently be given as |
| 68 | ``'rb'``, ``'wb'``, and ``'ab'`` respectively. |
| 69 | |
| 70 | If *filename* is a file object (rather than an actual file name), a mode of |
| 71 | ``'w'`` does not truncate the file, and is instead equivalent to ``'a'``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 72 | |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 73 | The *buffering* argument is ignored. Its use is deprecated. |
| 74 | |
Nadeem Vawda | 200e00a | 2011-05-27 01:52:16 +0200 | [diff] [blame] | 75 | If *mode* is ``'w'`` or ``'a'``, *compresslevel* can be a number between |
| 76 | ``1`` and ``9`` specifying the level of compression: ``1`` produces the |
| 77 | least compression, and ``9`` (default) produces the most compression. |
| 78 | |
| 79 | If *mode* is ``'r'``, the input file may be the concatenation of multiple |
| 80 | compressed streams. |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 81 | |
| 82 | :class:`BZ2File` provides all of the members specified by the |
| 83 | :class:`io.BufferedIOBase`, except for :meth:`detach` and :meth:`truncate`. |
| 84 | Iteration and the :keyword:`with` statement are supported. |
| 85 | |
| 86 | :class:`BZ2File` also provides the following method: |
| 87 | |
| 88 | .. method:: peek([n]) |
| 89 | |
| 90 | Return buffered data without advancing the file position. At least one |
| 91 | byte of data will be returned (unless at EOF). The exact number of bytes |
| 92 | returned is unspecified. |
| 93 | |
| 94 | .. versionadded:: 3.3 |
Benjamin Peterson | e0124bd | 2009-03-09 21:04:33 +0000 | [diff] [blame] | 95 | |
Benjamin Peterson | 10745a9 | 2009-03-09 21:08:47 +0000 | [diff] [blame] | 96 | .. versionchanged:: 3.1 |
Benjamin Peterson | e0124bd | 2009-03-09 21:04:33 +0000 | [diff] [blame] | 97 | Support for the :keyword:`with` statement was added. |
| 98 | |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 99 | .. versionchanged:: 3.3 |
| 100 | The :meth:`fileno`, :meth:`readable`, :meth:`seekable`, :meth:`writable`, |
| 101 | :meth:`read1` and :meth:`readinto` methods were added. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 102 | |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 103 | .. versionchanged:: 3.3 |
Nadeem Vawda | aebcdba | 2012-06-04 23:31:20 +0200 | [diff] [blame] | 104 | Support was added for *filename* being a :term:`file object` instead of an |
| 105 | actual filename. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 106 | |
Nadeem Vawda | 200e00a | 2011-05-27 01:52:16 +0200 | [diff] [blame] | 107 | .. versionchanged:: 3.3 |
| 108 | The ``'a'`` (append) mode was added, along with support for reading |
| 109 | multi-stream files. |
| 110 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 111 | |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 112 | Incremental (de)compression |
| 113 | --------------------------- |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 114 | |
Georg Brandl | 0d8f073 | 2009-04-05 22:20:44 +0000 | [diff] [blame] | 115 | .. class:: BZ2Compressor(compresslevel=9) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 116 | |
| 117 | Create a new compressor object. This object may be used to compress data |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 118 | incrementally. For one-shot compression, use the :func:`compress` function |
| 119 | instead. |
| 120 | |
| 121 | *compresslevel*, if given, must be a number between ``1`` and ``9``. The |
| 122 | default is ``9``. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 123 | |
Benjamin Peterson | e41251e | 2008-04-25 01:59:09 +0000 | [diff] [blame] | 124 | .. method:: compress(data) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 125 | |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 126 | Provide data to the compressor object. Returns a chunk of compressed data |
| 127 | if possible, or an empty byte string otherwise. |
| 128 | |
| 129 | When you have finished providing data to the compressor, call the |
| 130 | :meth:`flush` method to finish the compression process. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 131 | |
| 132 | |
Benjamin Peterson | e41251e | 2008-04-25 01:59:09 +0000 | [diff] [blame] | 133 | .. method:: flush() |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 134 | |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 135 | Finish the compression process. Returns the compressed data left in |
| 136 | internal buffers. |
| 137 | |
| 138 | The compressor object may not be used after this method has been called. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 139 | |
| 140 | |
| 141 | .. class:: BZ2Decompressor() |
| 142 | |
| 143 | Create a new decompressor object. This object may be used to decompress data |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 144 | incrementally. For one-shot compression, use the :func:`decompress` function |
| 145 | instead. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 146 | |
Nadeem Vawda | 200e00a | 2011-05-27 01:52:16 +0200 | [diff] [blame] | 147 | .. note:: |
| 148 | This class does not transparently handle inputs containing multiple |
| 149 | compressed streams, unlike :func:`decompress` and :class:`BZ2File`. If |
| 150 | you need to decompress a multi-stream input with :class:`BZ2Decompressor`, |
| 151 | you must use a new decompressor for each stream. |
| 152 | |
Benjamin Peterson | e41251e | 2008-04-25 01:59:09 +0000 | [diff] [blame] | 153 | .. method:: decompress(data) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 154 | |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 155 | Provide data to the decompressor object. Returns a chunk of decompressed |
| 156 | data if possible, or an empty byte string otherwise. |
| 157 | |
Nadeem Vawda | 200e00a | 2011-05-27 01:52:16 +0200 | [diff] [blame] | 158 | Attempting to decompress data after the end of the current stream is |
| 159 | reached raises an :exc:`EOFError`. If any data is found after the end of |
| 160 | the stream, it is ignored and saved in the :attr:`unused_data` attribute. |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 161 | |
| 162 | |
| 163 | .. attribute:: eof |
| 164 | |
| 165 | True if the end-of-stream marker has been reached. |
| 166 | |
| 167 | .. versionadded:: 3.3 |
| 168 | |
| 169 | |
| 170 | .. attribute:: unused_data |
| 171 | |
| 172 | Data found after the end of the compressed stream. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 173 | |
Nadeem Vawda | 200e00a | 2011-05-27 01:52:16 +0200 | [diff] [blame] | 174 | If this attribute is accessed before the end of the stream has been |
| 175 | reached, its value will be ``b''``. |
| 176 | |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 177 | |
| 178 | One-shot (de)compression |
| 179 | ------------------------ |
| 180 | |
Georg Brandl | 0d8f073 | 2009-04-05 22:20:44 +0000 | [diff] [blame] | 181 | .. function:: compress(data, compresslevel=9) |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 182 | |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 183 | Compress *data*. |
| 184 | |
| 185 | *compresslevel*, if given, must be a number between ``1`` and ``9``. The |
| 186 | default is ``9``. |
| 187 | |
| 188 | For incremental compression, use a :class:`BZ2Compressor` instead. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 189 | |
| 190 | |
| 191 | .. function:: decompress(data) |
| 192 | |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 193 | Decompress *data*. |
| 194 | |
Nadeem Vawda | 200e00a | 2011-05-27 01:52:16 +0200 | [diff] [blame] | 195 | If *data* is the concatenation of multiple compressed streams, decompress |
| 196 | all of the streams. |
| 197 | |
Antoine Pitrou | 37dc5f8 | 2011-04-03 17:05:46 +0200 | [diff] [blame] | 198 | For incremental decompression, use a :class:`BZ2Decompressor` instead. |
Georg Brandl | 116aa62 | 2007-08-15 14:28:22 +0000 | [diff] [blame] | 199 | |
Nadeem Vawda | 200e00a | 2011-05-27 01:52:16 +0200 | [diff] [blame] | 200 | .. versionchanged:: 3.3 |
| 201 | Support for multi-stream inputs was added. |
| 202 | |