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