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
orbytes
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 anio.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.
- exception gzip.BadGzipFile¶
An exception raised for invalid gzip files. It inherits from
OSError
.EOFError
andzlib.error
can also be raised for invalid gzip files.Added in version 3.8.
- 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, an
io.BytesIO
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 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'
. In future Python releases the mode of fileobj will not be used. It is better to always specify mode for writing.Note that the file is always opened in binary mode. To open a compressed file in text mode, use
open()
(or wrap yourGzipFile
with anio.TextIOWrapper
).The compresslevel argument is an integer from
0
to9
controlling the level of compression;1
is fastest and produces the least compression, and9
is slowest and produces the most compression.0
is no compression. The default is9
.The optional mtime argument is the timestamp requested by gzip. The time is in Unix format, i.e., seconds since 00:00:00 UTC, January 1, 1970. If mtime is omitted or
None
, the current time is used. Use mtime = 0 to generate a compressed stream that does not depend on creation time.See below for the
mtime
attribute that is set when decompressing.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 anio.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 thetruncate()
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 theGzipFile
, it may change the position of the underlying file object (e.g. if theGzipFile
was constructed with the fileobj parameter).Added in version 3.2.
- mode¶
'rb'
for reading and'wb'
for writing.Changed in version 3.13: In previous versions it was an integer
1
or2
.
- mtime¶
When decompressing, this attribute is set to the last timestamp in the most recently read header. It is an integer, holding the number of seconds since the Unix epoch (00:00:00 UTC, January 1, 1970). The initial value before reading any headers is
None
.
- name¶
The path to the gzip file on disk, as a
str
orbytes
. Equivalent to the output ofos.fspath()
on the original input path, with no other normalization, resolution or expansion.
Changed in version 3.1: Support for the
with
statement was added, along with the mtime constructor argument andmtime
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 ofNone
.Changed in version 3.6: Accepts a path-like object.
Deprecated since version 3.9: Opening
GzipFile
for writing without specifying the mode argument is deprecated.Changed in version 3.12: Remove the
filename
attribute, use thename
attribute instead.
- gzip.compress(data, compresslevel=9, *, mtime=None)¶
Compress the data, returning a
bytes
object containing the compressed data. compresslevel and mtime have the same meaning as in theGzipFile
constructor above.Added in version 3.2.
Changed in version 3.8: Added the mtime parameter for reproducible output.
Changed in version 3.11: Speed is improved by compressing all data at once instead of in a streamed fashion. Calls with mtime set to
0
are delegated tozlib.compress()
for better speed. In this situation the output may contain a gzip header “OS” byte value other than 255 “unknown” as supplied by the underlying zlib implementation.Changed in version 3.13: The gzip header OS byte is guaranteed to be set to 255 when this function is used as was the case in 3.10 and earlier.
- gzip.decompress(data)¶
Decompress the data, returning a
bytes
object containing the uncompressed data. This function is capable of decompressing multi-member gzip data (multiple gzip blocks concatenated together). When the data is certain to contain only one member thezlib.decompress()
function with wbits set to 31 is faster.Added in version 3.2.
Changed in version 3.11: Speed is improved by decompressing members at once in memory instead of in a streamed fashion.
Examples of usage¶
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
- Module
zlib
The basic data compression module needed to support the gzip file format.
Command Line Interface¶
The gzip
module provides a simple command line interface to compress or
decompress files.
Once executed the gzip
module keeps the input file(s).
Changed in version 3.8: Add a new command line interface with a usage. By default, when you will execute the CLI, the default compression level is 6.
Command line options¶
- --fast¶
Indicates the fastest compression method (less compression).
- --best¶
Indicates the slowest compression method (best compression).
- -d, --decompress¶
Decompress the given file.
- -h, --help¶
Show the help message.