56 lines
1.9 KiB
TeX
56 lines
1.9 KiB
TeX
|
% 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}
|