12.2. gzip
— Support for gzip files¶
Source code: Lib/gzip.py
This module provides a simple interface to compress and decompress files just like the GNU programs gzip and gunzip would.
The data compression is provided by the zlib
module.
The gzip
module provides the GzipFile
class. The GzipFile
class reads and writes gzip-format files, automatically compressing
or decompressing the data so that 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.
For other archive formats, see the bz2
, zipfile
, and
tarfile
modules.
The module defines the following items:
-
class
gzip.
GzipFile
(filename=None, mode=None, compresslevel=9, fileobj=None, mtime=None)¶ Constructor for the
GzipFile
class, which simulates most of the methods of a file object, with the exception of thetruncate()
method. 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 toNone
, 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'
. 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
1
to9
controlling the level of compression;1
is fastest and produces the least compression, and9
is slowest and produces the most compression. The default is9
.The mtime argument is an optional numeric timestamp to be written to the stream when compressing. All gzip compressed streams are required to contain a timestamp. If omitted or
None
, the current time is used. This module ignores the timestamp when decompressing; however, some programs, such as gunzip, make use of it. The format of the timestamp is the same as that of the return value oftime.time()
and of thest_mtime
attribute of the object returned byos.stat()
.Calling a
GzipFile
object’sclose()
method does not close fileobj, since you might wish to append more material after the compressed data. This also allows you to pass aio.BytesIO
object opened for writing as fileobj, and retrieve the resulting memory buffer using theio.BytesIO
object’sgetvalue()
method.GzipFile
supports theio.BufferedIOBase
interface, including iteration and thewith
statement. Only theread1()
andtruncate()
methods aren’t implemented.GzipFile
also provides the following method:-
peek
([n])¶ Read n uncompressed bytes without advancing the file position. At most one single read on the compressed stream is done to satisfy the call. The number of bytes returned may be more or less than requested.
New in version 3.2:
New in version 3.2.
-
Changed in version 3.1:
Changed in version 3.1: Support for the with
statement was added.
Changed in version 3.2:
Changed in version 3.2: Support for zero-padded files was added.
Changed in version 3.2:
Changed in version 3.2: Support for unseekable files was added.
-
gzip.
open
(filename, mode='rb', compresslevel=9)¶ This is a shorthand for
GzipFile(filename,
mode,
compresslevel)
. The filename argument is required; mode defaults to'rb'
and compresslevel defaults to9
.