New submission from David Albert Torpey <dt...@users.sourceforge.net>:
The purpose of the start argument in str.find() and str.rfind() is to allow for
repeated searches.
>>> def find_third_occurrence(s, value):
... p = s.find(value)
... p = s.find(value, p+1)
... return s.find(value, p+1)
...
>>> find_third_occurrence('scientific american', 'c')
16
The rfind() method is meant for searching from the right, but its start
argument is used internally as if it were searching from the left. This bug
makes it useless for repeated searches from the right.
>>> 'scientific american'.rfind('c')
16
>>> 'scientific american'.rfind('c', 15)
16
>>> 'scientific american'.rfind('c', 14)
16
Having found the first 'c' from the right at position 16, there is no way to
tell it to search further from the right and find the second 'c' at position 9.
----------
components: Interpreter Core
messages: 104375
nosy: dtorp
priority: normal
severity: normal
status: open
title: Start argument for str.rfind used incorrectly
type: behavior
versions: Python 2.6, Python 3.1
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue8551>
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