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author | Fred Drake <fdrake@acm.org> | 1998-04-28 18:28:21 (GMT) |
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committer | Fred Drake <fdrake@acm.org> | 1998-04-28 18:28:21 (GMT) |
commit | ca6b4fe36b71c64b3f7cbf533bcf3be8765cc66b (patch) | |
tree | a9c636db350c0d38d5e994b0ba68f84b1084c7d7 /Doc/lib/libbisect.tex | |
parent | 188a8471b8bc3ebbc0ebfc1e5096af443032d4bd (diff) | |
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Section for bisect module.
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-rw-r--r-- | Doc/lib/libbisect.tex | 55 |
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diff --git a/Doc/lib/libbisect.tex b/Doc/lib/libbisect.tex new file mode 100644 index 0000000..81cb550 --- /dev/null +++ b/Doc/lib/libbisect.tex @@ -0,0 +1,55 @@ +% LaTeX produced by Fred L. Drake, Jr. <fdrake@acm.org>, with an +% example based on the PyModules FAQ entry by Aaron Watters +% <arw@pythonpros.com>. + +\section{Standard Module \module{bisect}} +\stmodindex{bisect} +\label{module-bisect} + + +This module provides support for maintaining a list in sorted order +without having to sort the list after each insertion. For long lists +of items with expensive comparison operations, this can be an +improvement over the more common approach. The module is called +\module{bisect} because it uses a basic bisection algorithm to do its +work. The source code may be used a useful reference for a working +example of the algorithm (i.e., the boundary conditions are already +right!). + +The following functions are provided: + +\begin{funcdesc}{bisect}{list, item\optional{, lo\optional{, hi}}} +Locate the proper insertion point for \var{item} in \var{list} to +maintain sorted order. The parameters \var{lo} and \var{hi} may be +used to specify a subset of the list which should be considered. The +return value is suitable for use as the first parameter to +\code{\var{list}.insert()}. +\end{funcdesc} + +\begin{funcdesc}{insort}{list, item\optional{, lo\optional{, hi}}} +Insert \var{item} in \var{list} in sorted order. This is equivalent +to \code{\var{list}.insert(bisect.bisect(\var{list}, \var{item}, +\var{lo}, \var{hi}), \var{item})}. +\end{funcdesc} + + +\subsection{Example} +\nodename{bisect-example} + +The \function{bisect()} function is generally useful for categorizing +numeric data. This example uses \function{bisect()} to look up a +letter grade for an exam total (say) based on a set of ordered numeric +breakpoints: 85 and up is an `A', 75..84 is a `B', etc. + +\begin{verbatim} +>>> grades = "FEDCBA" +>>> breakpoints = [30, 44, 66, 75, 85] +>>> from bisect import bisect +>>> def grade(total): +... return grades[bisect(breakpoints, total)] +... +>>> grade(66) +'C' +>>> map(grade, [33, 99, 77, 44, 12, 88]) +['E', 'A', 'B', 'D', 'F', 'A'] +\end{verbatim} |