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+\section{Built-in Module \sectcode{gzip}}
+\label{module-gzip}
+\bimodindex{gzip}
+
+The data compression provided by the \code{zlib} module is compatible
+with that used by the GNU compression program \file{gzip}.
+Accordingly, the \code{gzip} module provides the \code{GzipFile} class
+to read and write \file{gzip}-format files, automatically compressing
+or decompressing the data so it looks like an ordinary file object.
+
+\code{GzipFile} objects simulate most of the methods of a file
+object, though it's not possible to use the \code{seek()} and
+\code{tell()} methods to access the file randomly.
+
+\renewcommand{\indexsubitem}{(in module gzip)}
+\begin{funcdesc}{open}{fileobj\optional{\, filename\optional{\, mode\, compresslevel}}}
+ Returns a new \code{GzipFile} object on top of \var{fileobj}, which
+ can be a regular file, a \code{StringIO} object, or any object which
+ simulates a file.
+
+ The \file{gzip} file format includes the original filename of the
+ uncompressed file; when opening a \code{GzipFile} object for
+ writing, it can be set by the \var{filename} argument. The default
+ value is \code{"GzippedFile"}.
+
+ \var{mode} can be either \code{'r'} or \code{'w'} depending on
+ whether the file will be read or written. \var{compresslevel} is an
+ integer from 1 to 9 controlling the level of compression; 1 is
+ fastest and produces the least compression, and 9 is slowest and
+ produces the most compression. The default value of
+ \var{compresslevel} is 9.
+
+ Calling a \code{GzipFile} object's \code{close()} method does not
+ close \var{fileobj}, since you might wish to append more material
+ after the compressed data. This also allows you to pass a
+ \code{StringIO} object opened for writing as \var{fileobj}, and
+ retrieve the resulting memory buffer using the \code{StringIO}
+ object's \code{getvalue()} method.
+\end{funcdesc}
+
+\begin{seealso}
+\seemodule{zlib}{the basic data compression module}
+\end{seealso}
+