45 lines
1.9 KiB
TeX
45 lines
1.9 KiB
TeX
\section{Built-in Module \sectcode{gzip}}
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\label{module-gzip}
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\bimodindex{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 \file{gzip}.
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Accordingly, the \code{gzip} module provides the \code{GzipFile} class
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to read and write \file{gzip}-format files, automatically compressing
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or decompressing the data so it looks like an ordinary file object.
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\code{GzipFile} objects simulate most of the methods of a file
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object, though it's not possible to use the \code{seek()} and
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\code{tell()} methods to access the file randomly.
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\setindexsubitem{(in module gzip)}
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\begin{funcdesc}{open}{fileobj\optional{\, filename\optional{\, mode\, compresslevel}}}
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Returns a new \code{GzipFile} object on top of \var{fileobj}, which
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can be a regular file, a \code{StringIO} object, or any object which
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simulates a file.
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The \file{gzip} file format includes the original filename of the
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uncompressed file; when opening a \code{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 1 to 9 controlling the level of compression; 1 is
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fastest and produces the least compression, and 9 is slowest and
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produces the most compression. The default value of
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\var{compresslevel} is 9.
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Calling a \code{GzipFile} object's \code{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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\code{StringIO} object opened for writing as \var{fileobj}, and
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retrieve the resulting memory buffer using the \code{StringIO}
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object's \code{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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