7.14 gzip -- Gestión de ficheros gzip

La compresión de datos proporcionada por el módulo zlib es compatible con la utilizada por el compresor de GNU, gzip. Además, el módulo gzip proporciona la clase GzipFile para leer y escribir ficheros de formato gzip, comprimiendo y descomprimiendo transparentemente los datos para que los ficheros parezcan normales (sin comprimir). Hay que destacar que otros formatos de compresión que los programas gzip y gunzip manejan perfectamente no están dentro de los gestionados por esta biblioteca. En concreto, este programa no gestiona los formatos producidos por compress ni pack.

Este módule define los siguientes elementos:

GzipFile ([filename[, mode[, compresslevel[, fileobj]]]])
Constructor for the GzipFile class, which simulates most of the methods of a file object, with the exception of the seek() and tell() methods. At least one of fileobj and filename must be given a non-trivial value.

The new class instance is based on fileobj, which can be a regular file, a StringIO object, or any other object which simulates a file. It defaults to None, in which case filename is opened to provide a file object.

When fileobj is not None, the filename argument is only used to be included in the gzip file header, which may includes the original filename of the uncompressed file. It defaults to the filename of fileobj, if discernible; otherwise, it defaults to the empty string, and in this case the original filename is not included in the header.

The mode argument can be any of 'r', 'rb', 'a', 'ab', 'w', or 'wb', depending on whether the file will be read or written. The default is the mode of fileobj if discernible; otherwise, the default is 'rb'. Be aware that only the 'rb', 'ab', and 'wb' values should be used for cross-platform portability.

The compresslevel argument is an integer from 1 to 9 controlling the level of compression; 1 is fastest and produces the least compression, and 9 is slowest and produces the most compression. The default is 9.

Calling a GzipFile object's close() method does not close fileobj, since you might wish to append more material after the compressed data. This also allows you to pass a StringIO object opened for writing as fileobj, and retrieve the resulting memory buffer using the StringIO object's getvalue() method.

open (filename[, mode[, compresslevel]])
This is a shorthand for GzipFile(filename, mode, compresslevel). The filename argument is required; mode defaults to 'rb' and compresslevel defaults to 9.

Más informació en:

Module zlib:
the basic data compression module.

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