# 13.3. `bz2` — Suporte para compressão bzip2

Código Fonte: Lib/bz2.py

Este módulo fornece uma interface abrangente para compactar e descompactar dados usando o algoritmo de compactação bzip2

O módulo `bz2` contém:

- The `open()` function and `BZ2File` class for reading and writing compressed files.

- The `BZ2Compressor` and `BZ2Decompressor` classes for incremental (de)compression.

- The `compress()` and `decompress()` functions for one-shot (de)compression.

All of the classes in this module may safely be accessed from multiple threads.

## 13.3.1. (Des)compressão de arquivos

`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.

  Para o modo binário, esta função é equivalente a `BZ2File` constructor: `BZ2File(filename, mode, compresslevel=compresslevel)`. Neste caso, os argumentos encoding, errors e newline não devem ser fornecidos.

  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).

  Novo na versão 3.3.

  Alterado na versão 3.4: The `'x'` (exclusive creation) mode was added.

  Alterado na versão 3.6: Aceita um 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` 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.

    Nota

    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).

    Novo na versão 3.3.

  Alterado na versão 3.1: Suporte para a instrução `with` foi adicionado.

  Alterado na versão 3.3: The `fileno()`, `readable()`, `seekable()`, `writable()`, `read1()` and `readinto()` methods were added.

  Alterado na versão 3.3: Support was added for filename being a file object instead of an actual filename.

  Alterado na versão 3.3: The `'a'` (append) mode was added, along with support for reading multi-stream files.

  Alterado na versão 3.4: The `'x'` (exclusive creation) mode was added.

  Alterado na versão 3.5: The `read()` method now accepts an argument of `None`.

  Alterado na versão 3.6: Aceita um path-like object.

## 13.3.2. (Des)compressão incremental

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` 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.

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.

  Nota

  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.

    Alterado na versão 3.5: Added the max_length parameter.

  `eof`

    `True` if the end-of-stream marker has been reached.

    Novo na versão 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.

    Novo na versão 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` 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.

  Alterado na versão 3.3: Support for multi-stream inputs was added.