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Add example of how to do key lookups with bisect().

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Raymond Hettinger 2009-06-11 22:04:00 +00:00
parent 3bca523a8c
commit 87be88c2e9
1 changed files with 18 additions and 0 deletions
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18
Doc/library/bisect.rst
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@ -85,4 +85,22 @@ is a 'B', etc.
>>> map(grade, [33, 99, 77, 44, 12, 88]) >>> map(grade, [33, 99, 77, 44, 12, 88])
['E', 'A', 'B', 'D', 'F', 'A'] ['E', 'A', 'B', 'D', 'F', 'A']
Unlike the :func:`sorted` function, it does not make sense for the :func:`bisect`
functions to have *key* or *reversed* arguments because that would lead to an
inefficent design (successive calls to bisect functions would not "remember"
all of the previous key lookups).
Instead, it is better to search a list of precomputed keys to find the index
of the record in question::
>>> data = [('red', 5), ('blue', 1), ('yellow', 8), ('black', 0)]
>>> data.sort(key=lambda r: r[1]) # precomputed list of keys
>>> keys = [r[1] for r in data]
>>> data[bisect_left(keys, 0)]
('black', 0)
>>> data[bisect_left(keys, 1)]
('blue', 1)
>>> data[bisect_left(keys, 5)]
('red', 5)
>>> data[bisect_left(keys, 8)]
('yellow', 8)