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Add more itertool recipes (GH-28165)

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(cherry picked from commit 750368cbcd)

Co-authored-by: Raymond Hettinger <rhettinger@users.noreply.github.com>
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Miss Islington (bot) 2021-09-07 10:52:26 -07:00 • committed by GitHub
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2 changed files with 43 additions and 2 deletions
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22
Doc/library/itertools.rst
View file

@ -492,6 +492,8 @@ loops that truncate the stream.
next(b, None) next(b, None)
return zip(a, b) return zip(a, b)
.. versionadded:: 3.10
.. function:: permutations(iterable, r=None) .. function:: permutations(iterable, r=None)
@ -812,11 +814,27 @@ which incur interpreter overhead.
return starmap(func, repeat(args, times)) return starmap(func, repeat(args, times))
def grouper(iterable, n, fillvalue=None): def grouper(iterable, n, fillvalue=None):
"Collect data into fixed-length chunks or blocks" "Collect data into non-overlapping fixed-length chunks or blocks"
# grouper('ABCDEFG', 3, 'x') --> ABC DEF Gxx" # grouper('ABCDEFG', 3, 'x') --> ABC DEF Gxx
args = [iter(iterable)] * n args = [iter(iterable)] * n
return zip_longest(*args, fillvalue=fillvalue) return zip_longest(*args, fillvalue=fillvalue)
def triplewise(iterable):
"Return overlapping triplets from an iterable"
# pairwise('ABCDEFG') -> ABC BCD CDE DEF EFG
for (a, _), (b, c) in pairwise(pairwise(iterable)):
yield a, b, c
def sliding_window(iterable, n):
# sliding_window('ABCDEFG', 4) -> ABCD BCDE CDEF DEFG
it = iter(iterable)
window = deque(islice(it, n), maxlen=n)
if len(window) == n:
yield tuple(window)
for x in it:
window.append(x)
yield tuple(window)
def roundrobin(*iterables): def roundrobin(*iterables):
"roundrobin('ABC', 'D', 'EF') --> A D E B F C" "roundrobin('ABC', 'D', 'EF') --> A D E B F C"
# Recipe credited to George Sakkis # Recipe credited to George Sakkis

23
Lib/test/test_itertools.py
View file

@ -2393,6 +2393,23 @@ def test_permutations_sizeof(self):
... else: ... else:
... return starmap(func, repeat(args, times)) ... return starmap(func, repeat(args, times))
>>> def triplewise(iterable):
... "Return overlapping triplets from an iterable"
... # pairwise('ABCDEFG') -> ABC BCD CDE DEF EFG
... for (a, _), (b, c) in pairwise(pairwise(iterable)):
... yield a, b, c
>>> import collections
>>> def sliding_window(iterable, n):
... # sliding_window('ABCDEFG', 4) -> ABCD BCDE CDEF DEFG
... it = iter(iterable)
... window = collections.deque(islice(it, n), maxlen=n)
... if len(window) == n:
... yield tuple(window)
... for x in it:
... window.append(x)
... yield tuple(window)
>>> def grouper(n, iterable, fillvalue=None): >>> def grouper(n, iterable, fillvalue=None):
... "grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx" ... "grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx"
... args = [iter(iterable)] * n ... args = [iter(iterable)] * n
@ -2569,6 +2586,12 @@ def test_permutations_sizeof(self):
>>> list(grouper(3, 'abcdefg', 'x')) >>> list(grouper(3, 'abcdefg', 'x'))
[('a', 'b', 'c'), ('d', 'e', 'f'), ('g', 'x', 'x')] [('a', 'b', 'c'), ('d', 'e', 'f'), ('g', 'x', 'x')]
>>> list(triplewise('ABCDEFG'))
[('A', 'B', 'C'), ('B', 'C', 'D'), ('C', 'D', 'E'), ('D', 'E', 'F'), ('E', 'F', 'G')]
>>> list(sliding_window('ABCDEFG', 4))
[('A', 'B', 'C', 'D'), ('B', 'C', 'D', 'E'), ('C', 'D', 'E', 'F'), ('D', 'E', 'F', 'G')]
>>> list(roundrobin('abc', 'd', 'ef')) >>> list(roundrobin('abc', 'd', 'ef'))
['a', 'd', 'e', 'b', 'f', 'c'] ['a', 'd', 'e', 'b', 'f', 'c']