New submission from Paul Ianas:
The precondition for all the bisect functions is implemented like this:
if lo < 0:
raise ValueError('lo must be non-negative')
if hi is None:
hi = len(a)
Now, of course, if hi is given, and hi >= 2 * len(a), then we get an
IndexError. In case hi < 0, we always get 0 as a result (even if the element is
there).
I think it would be better to treat the hi in the precondition in the same way
as the lo parameter: that means, raise a ValueError in case hi has an illegal
value.
Disclaimer: of course, it makes no sense to give an illegal argument to that
function; still, since lo is treated against illegal values, maybe it's better
to do the same for hi.
At the same time, maybe moving the precondition code in a separate function
(which raises a ValueError in case precondition is not met) makes more sense,
for not repeating the same code in all bisect functions.
A small snippet which reproduces this:
from bisect import bisect_left
a = [1, 2, 3, 4]
idx = bisect_left(a, 2, 0, 10) # 10 > 2 * 4
print(idx)
----------
components: Library (Lib)
messages: 229750
nosy: Paul.Ianas
priority: normal
severity: normal
status: open
title: bisect index out of bounds issue
type: enhancement
versions: Python 2.7, Python 3.2, Python 3.3, Python 3.4, Python 3.5
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue22683>
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