Guido van Rossum | 41884a9 | 1997-07-17 16:26:11 +0000 | [diff] [blame^] | 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 | |