126 lines
4.0 KiB
TeX
126 lines
4.0 KiB
TeX
\section{\module{StringIO} ---
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Read and write strings as files}
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\declaremodule{standard}{StringIO}
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\modulesynopsis{Read and write strings as if they were files.}
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This module implements a file-like class, \class{StringIO},
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that reads and writes a string buffer (also known as \emph{memory
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files}). See the description of file objects for operations (section
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\ref{bltin-file-objects}).
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\begin{classdesc}{StringIO}{\optional{buffer}}
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When a \class{StringIO} object is created, it can be initialized
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to an existing string by passing the string to the constructor.
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If no string is given, the \class{StringIO} will start empty.
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In both cases, the initial file position starts at zero.
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The \class{StringIO} object can accept either Unicode or 8-bit
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strings, but mixing the two may take some care. If both are used,
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8-bit strings that cannot be interpreted as 7-bit \ASCII{} (that
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use the 8th bit) will cause a \exception{UnicodeError} to be raised
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when \method{getvalue()} is called.
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\end{classdesc}
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The following methods of \class{StringIO} objects require special
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mention:
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\begin{methoddesc}{getvalue}{}
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Retrieve the entire contents of the ``file'' at any time before the
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\class{StringIO} object's \method{close()} method is called. See the
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note above for information about mixing Unicode and 8-bit strings;
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such mixing can cause this method to raise \exception{UnicodeError}.
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\end{methoddesc}
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\begin{methoddesc}{close}{}
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Free the memory buffer.
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\end{methoddesc}
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Example usage:
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\begin{verbatim}
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import StringIO
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output = StringIO.StringIO()
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output.write('First line.\n')
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print >>output, 'Second line.'
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# Retrieve file contents -- this will be
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# 'First line.\nSecond line.\n'
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contents = output.getvalue()
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# Close object and discard memory buffer --
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# .getvalue() will now raise an exception.
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output.close()
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\end{verbatim}
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\section{\module{cStringIO} ---
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Faster version of \module{StringIO}}
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\declaremodule{builtin}{cStringIO}
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\modulesynopsis{Faster version of \module{StringIO}, but not
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subclassable.}
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\moduleauthor{Jim Fulton}{jim@zope.com}
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\sectionauthor{Fred L. Drake, Jr.}{fdrake@acm.org}
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The module \module{cStringIO} provides an interface similar to that of
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the \refmodule{StringIO} module. Heavy use of \class{StringIO.StringIO}
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objects can be made more efficient by using the function
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\function{StringIO()} from this module instead.
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Since this module provides a factory function which returns objects of
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built-in types, there's no way to build your own version using
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subclassing. Use the original \refmodule{StringIO} module in that case.
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Unlike the memory files implemented by the \refmodule{StringIO}
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module, those provided by this module are not able to accept Unicode
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strings that cannot be encoded as plain \ASCII{} strings.
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Calling \function{StringIO()} with a Unicode string parameter populates
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the object with the buffer representation of the Unicode string, instead of
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encoding the string.
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Another difference from the \refmodule{StringIO} module is that calling
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\function{StringIO()} with a string parameter creates a read-only object.
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Unlike an object created without a string parameter, it does not have
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write methods. These objects are not generally visible. They turn up in
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tracebacks as \class{StringI} and \class{StringO}.
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The following data objects are provided as well:
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\begin{datadesc}{InputType}
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The type object of the objects created by calling
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\function{StringIO} with a string parameter.
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\end{datadesc}
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\begin{datadesc}{OutputType}
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The type object of the objects returned by calling
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\function{StringIO} with no parameters.
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\end{datadesc}
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There is a C API to the module as well; refer to the module source for
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more information.
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Example usage:
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\begin{verbatim}
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import cStringIO
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output = cStringIO.StringIO()
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output.write('First line.\n')
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print >>output, 'Second line.'
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# Retrieve file contents -- this will be
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# 'First line.\nSecond line.\n'
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contents = output.getvalue()
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# Close object and discard memory buffer --
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# .getvalue() will now raise an exception.
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output.close()
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\end{verbatim}
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