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, as well as the
open(), compress() and decompress() convenience functions.
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.
The module defines the following items:
gzip.open(filename, mode='rb', compresslevel=9, encoding=None, errors=None, newline=None)¶Open a gzip-compressed file in binary or text mode, returning a file object.
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', 'a', 'ab',
'w', 'wb', 'x' or 'xb' for binary mode, or 'rt',
'at', 'wt', or 'xt' for text mode. The default is 'rb'.
The compresslevel argument is an integer from 0 to 9, as for the
GzipFile constructor.
For binary mode, this function is equivalent to the GzipFile
constructor: GzipFile(filename, mode, compresslevel). In this case, the
encoding, errors and newline arguments must not be provided.
For text mode, a GzipFile object is created, and wrapped in an
io.TextIOWrapper instance with the specified encoding, error
handling behavior, and line ending(s).
Changed in version 3.3: Added support for filename being a file object, support for text mode, and the encoding, errors and newline arguments.
Changed in version 3.4: Added support for the 'x', 'xb' and 'xt' modes.
Changed in version 3.6: Accepts a path-like object.
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 the truncate()
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, an
io.BytesIO 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 include 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',
'wb', 'x', or 'xb', depending on whether the file will be read or
written. The default is the mode of fileobj if discernible; otherwise, the
default is 'rb'.
Note that the file is always opened in binary mode. To open a compressed file
in text mode, use open() (or wrap your GzipFile with an
io.TextIOWrapper).
The compresslevel argument is an integer from 0 to 9 controlling
the level of compression; 1 is fastest and produces the least
compression, and 9 is slowest and produces the most compression. 0
is no compression. The default is 9.
The mtime argument is an optional numeric timestamp to be written to
the last modification time field in the stream when compressing. It
should only be provided in compression mode. If omitted or None, the
current time is used. See the mtime attribute for more details.
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 an io.BytesIO object opened for
writing as fileobj, and retrieve the resulting memory buffer using the
io.BytesIO object’s getvalue() method.
GzipFile supports the io.BufferedIOBase interface,
including iteration and the with statement. Only the
truncate() method isn’t implemented.
GzipFile also provides the following method and attribute:
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.
Note
While calling peek() does not change the file position of
the GzipFile, it may change the position of the underlying
file object (e.g. if the GzipFile was constructed with the
fileobj parameter).
New in version 3.2.
mtime¶When decompressing, the value of the last modification time field in
the most recently read header may be read from this attribute, as an
integer. The initial value before reading any headers is None.
All gzip compressed streams are required to contain this
timestamp field. Some programs, such as gunzip, make use
of the timestamp. The format is the same as the return value of
time.time() and the st_mtime attribute of
the object returned by os.stat().
Changed in version 3.1: Support for the with statement was added, along with the
mtime constructor argument and mtime attribute.
Changed in version 3.2: Support for zero-padded and unseekable files was added.
Changed in version 3.3: The io.BufferedIOBase.read1() method is now implemented.
Changed in version 3.4: Added support for the 'x' and 'xb' modes.
Changed in version 3.5: Added support for writing arbitrary
bytes-like objects.
The read() method now accepts an argument of
None.
Changed in version 3.6: Accepts a path-like object.
gzip.compress(data, compresslevel=9)¶Compress the data, returning a bytes object containing
the compressed data. compresslevel has the same meaning as in
the GzipFile constructor above.
New in version 3.2.
gzip.decompress(data)¶Decompress the data, returning a bytes object containing the
uncompressed data.
New in version 3.2.
Example of how to read a compressed file:
import gzip
with gzip.open('/home/joe/file.txt.gz', 'rb') as f:
file_content = f.read()
Example of how to create a compressed GZIP file:
import gzip
content = b"Lots of content here"
with gzip.open('/home/joe/file.txt.gz', 'wb') as f:
f.write(content)
Example of how to GZIP compress an existing file:
import gzip
import shutil
with open('/home/joe/file.txt', 'rb') as f_in:
with gzip.open('/home/joe/file.txt.gz', 'wb') as f_out:
shutil.copyfileobj(f_in, f_out)
Example of how to GZIP compress a binary string:
import gzip
s_in = b"Lots of content here"
s_out = gzip.compress(s_in)
See also
zlib