13.2. 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, 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).Distinto en la versión 3.3: Added support for filename being a file object, support for text mode, and the encoding, errors and newline arguments.
Distinto en la versión 3.4: Added support for the
'x'
,'xb'
and'xt'
modes.
-
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'
.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 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 themtime
attribute for more details.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.
Nota
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).Nuevo en la versión 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 thest_mtime
attribute of the object returned byos.stat()
.
Distinto en la versión 3.1: Support for the
with
statement was added, along with the mtime constructor argument andmtime
attribute.Distinto en la versión 3.2: Support for zero-padded and unseekable files was added.
Distinto en la versión 3.3: The
io.BufferedIOBase.read1()
method is now implemented.Distinto en la versión 3.4: Added support for the
'x'
and'xb'
modes.Distinto en la versión 3.5: Added support for writing arbitrary bytes-like objects. The
read()
method now accepts an argument ofNone
.-
-
gzip.
compress
(data, compresslevel=9)¶ Compress the data, returning a
bytes
object containing the compressed data. compresslevel has the same meaning as in theGzipFile
constructor above.Nuevo en la versión 3.2.
-
gzip.
decompress
(data)¶ Decompress the data, returning a
bytes
object containing the uncompressed data.Nuevo en la versión 3.2.
13.2.1. 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)
Ver también
- Module
zlib
- The basic data compression module needed to support the gzip file format.