|
5814
|
1 \section{Built-in Module \sectcode{gzip}}
|
|
|
2 \label{module-gzip}
|
|
|
3 \bimodindex{gzip}
|
|
|
4
|
|
|
5 The data compression provided by the \code{zlib} module is compatible
|
|
|
6 with that used by the GNU compression program \file{gzip}.
|
|
|
7 Accordingly, the \code{gzip} module provides the \code{GzipFile} class
|
|
|
8 to read and write \file{gzip}-format files, automatically compressing
|
|
|
9 or decompressing the data so it looks like an ordinary file object.
|
|
|
10
|
|
|
11 \code{GzipFile} objects simulate most of the methods of a file
|
|
|
12 object, though it's not possible to use the \code{seek()} and
|
|
|
13 \code{tell()} methods to access the file randomly.
|
|
|
14
|
|
|
15 \renewcommand{\indexsubitem}{(in module gzip)}
|
|
|
16 \begin{funcdesc}{open}{fileobj\optional{\, filename\optional{\, mode\, compresslevel}}}
|
|
|
17 Returns a new \code{GzipFile} object on top of \var{fileobj}, which
|
|
|
18 can be a regular file, a \code{StringIO} object, or any object which
|
|
|
19 simulates a file.
|
|
|
20
|
|
|
21 The \file{gzip} file format includes the original filename of the
|
|
|
22 uncompressed file; when opening a \code{GzipFile} object for
|
|
|
23 writing, it can be set by the \var{filename} argument. The default
|
|
|
24 value is \code{"GzippedFile"}.
|
|
|
25
|
|
|
26 \var{mode} can be either \code{'r'} or \code{'w'} depending on
|
|
|
27 whether the file will be read or written. \var{compresslevel} is an
|
|
|
28 integer from 1 to 9 controlling the level of compression; 1 is
|
|
|
29 fastest and produces the least compression, and 9 is slowest and
|
|
|
30 produces the most compression. The default value of
|
|
|
31 \var{compresslevel} is 9.
|
|
|
32
|
|
|
33 Calling a \code{GzipFile} object's \code{close()} method does not
|
|
|
34 close \var{fileobj}, since you might wish to append more material
|
|
|
35 after the compressed data. This also allows you to pass a
|
|
|
36 \code{StringIO} object opened for writing as \var{fileobj}, and
|
|
|
37 retrieve the resulting memory buffer using the \code{StringIO}
|
|
|
38 object's \code{getvalue()} method.
|
|
|
39 \end{funcdesc}
|
|
|
40
|
|
|
41 \begin{seealso}
|
|
|
42 \seemodule{zlib}{the basic data compression module}
|
|
|
43 \end{seealso}
|
|
|
44
|
