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bpo-31942: Document optional support of start and stop attributes in Sequence.index method (GH-4277) (#4811) 

(cherry picked from commit 5ce0a2a100)
This commit is contained in:
Miss Islington (bot) 2017-12-12 02:58:26 -08:00 committed by Victor Stinner
parent ce5a3cd9b1
commit 78cd00b799
2 changed files with 6 additions and 3 deletions
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6
Doc/library/stdtypes.rst
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@ -973,9 +973,9 @@ Notes:
(8)
``index`` raises :exc:`ValueError` when *x* is not found in *s*.
When supported, the additional arguments to the index method allow
efficient searching of subsections of the sequence. Passing the extra
arguments is roughly equivalent to using ``s[i:j].index(x)``, only
Not all implementations support passing the additional arguments *i* and *j*.
These arguments allow efficient searching of subsections of the sequence. Passing
the extra arguments is roughly equivalent to using ``s[i:j].index(x)``, only
without copying any data and with the returned index being relative to
the start of the sequence rather than the start of the slice.

3
Lib/_collections_abc.py
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@ -899,6 +899,9 @@ class Sequence(Reversible, Collection):
def index(self, value, start=0, stop=None):
'''S.index(value, [start, [stop]]) -> integer -- return first index of value.
Raises ValueError if the value is not present.
Supporting start and stop arguments is optional, but
recommended.
'''
if start is not None and start < 0:
start = max(len(self) + start, 0)