The data compression provided by the
zlib module is compatible
with that used by the GNU compression program gzip.
Accordingly, the gzip module provides the GzipFile
class to read and write gzip-format files, automatically
compressing or decompressing the data so it looks like an ordinary
file object. Note that additional file formats which can be
decompressed by the gzip and gunzip programs, such
as those produced by compress and pack, are not
supported by this module.
The module defines the following items:
|[filename[, mode[, compresslevel[, fileobj]]]])|
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
'wb', depending on
whether the file will be read or written. The default is the mode of
fileobj if discernible; otherwise, the default is
If not given, the 'b' flag will be added to the mode to ensure the
file is opened in binary mode for cross-platform portability.
The compresslevel argument is an integer from
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
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.
|filename[, mode[, compresslevel]])|
compresslevel). The filename argument is required; mode defaults to
'rb'and compresslevel defaults to