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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}
+