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58 lines
1.6 KiB
TeX
58 lines
1.6 KiB
TeX
\section{\module{xreadlines} ---
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Efficient iteration over a file}
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\declaremodule{extension}{xreadlines}
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\modulesynopsis{Efficient iteration over the lines of a file.}
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\versionadded{2.1}
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This module defines a new object type which can efficiently iterate
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over the lines of a file. An xreadlines object is a sequence type
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which implements simple in-order indexing beginning at \code{0}, as
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required by \keyword{for} statement or the
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\function{filter()} function.
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Thus, the code
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\begin{verbatim}
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import xreadlines, sys
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for line in xreadlines.xreadlines(sys.stdin):
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pass
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\end{verbatim}
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has approximately the same speed and memory consumption as
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\begin{verbatim}
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while 1:
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lines = sys.stdin.readlines(8*1024)
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if not lines: break
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for line in lines:
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pass
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\end{verbatim}
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except the clarity of the \keyword{for} statement is retained in the
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former case.
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\begin{funcdesc}{xreadlines}{fileobj}
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Return a new xreadlines object which will iterate over the contents
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of \var{fileobj}. \var{fileobj} must have a \method{readlines()}
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method that supports the \var{sizehint} parameter. \note{Because
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the \method{readlines()} method buffers data, this effectively
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ignores the effects of setting the file object as unbuffered.}
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\end{funcdesc}
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An xreadlines object \var{s} supports the following sequence
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operation:
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\begin{tableii}{c|l}{code}{Operation}{Result}
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\lineii{\var{s}[\var{i}]}{\var{i}'th line of \var{s}}
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\end{tableii}
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If successive values of \var{i} are not sequential starting from
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\code{0}, this code will raise \exception{RuntimeError}.
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After the last line of the file is read, this code will raise an
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\exception{IndexError}.
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