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gh-118476: Fix corner cases in islice() rough equivalent. (Gh-118559)

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Raymond Hettinger 2024-05-05 01:42:30 -05:00 • committed by GitHub
parent fd0ea63f82
commit c7c9b913c0
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1 changed files with 11 additions and 18 deletions
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29
Doc/library/itertools.rst
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@ -504,24 +504,17 @@ loops that truncate the stream.
# islice('ABCDEFG', 2, None) → C D E F G # islice('ABCDEFG', 2, None) → C D E F G
# islice('ABCDEFG', 0, None, 2) → A C E G # islice('ABCDEFG', 0, None, 2) → A C E G
s = slice(*args) s = slice(*args)
start, stop, step = s.start or 0, s.stop or sys.maxsize, s.step or 1 start = 0 if s.start is None else s.start
it = iter(range(start, stop, step)) stop = s.stop
try: step = 1 if s.step is None else s.step
nexti = next(it) if start < 0 or (stop is not None and stop < 0) or step <= 0:
except StopIteration: raise ValueError
# Consume *iterable* up to the *start* position. indices = count() if stop is None else range(max(stop, start))
for i, element in zip(range(start), iterable): next_i = start
pass for i, element in zip(indices, iterable):
return if i == next_i:
try: yield element
for i, element in enumerate(iterable): next_i += step
if i == nexti:
yield element
nexti = next(it)
except StopIteration:
# Consume to *stop*.
for i, element in zip(range(i + 1, stop), iterable):
pass
.. function:: pairwise(iterable) .. function:: pairwise(iterable)