https://github.com/python/cpython/commit/e82f6dfae54170559fe46000fe6db9fee2a21a96
commit: e82f6dfae54170559fe46000fe6db9fee2a21a96
branch: main
author: Raymond Hettinger <[email protected]>
committer: rhettinger <[email protected]>
date: 2024-03-13T02:12:30-05:00
summary:
Modernize roundrobin() recipe and improve variable names (gh-116710)
files:
M Doc/library/itertools.rst
diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index 36e555d37d45de..26d5cdaff8c14f 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -932,31 +932,25 @@ which incur interpreter overhead.
# grouper('ABCDEFG', 3, fillvalue='x') --> ABC DEF Gxx
# grouper('ABCDEFG', 3, incomplete='strict') --> ABC DEF ValueError
# grouper('ABCDEFG', 3, incomplete='ignore') --> ABC DEF
- args = [iter(iterable)] * n
+ iterators = [iter(iterable)] * n
match incomplete:
case 'fill':
- return zip_longest(*args, fillvalue=fillvalue)
+ return zip_longest(*iterators, fillvalue=fillvalue)
case 'strict':
- return zip(*args, strict=True)
+ return zip(*iterators, strict=True)
case 'ignore':
- return zip(*args)
+ return zip(*iterators)
case _:
raise ValueError('Expected fill, strict, or ignore')
def roundrobin(*iterables):
"Visit input iterables in a cycle until each is exhausted."
# roundrobin('ABC', 'D', 'EF') --> A D E B F C
- # Recipe credited to George Sakkis
- num_active = len(iterables)
- nexts = cycle(iter(it).__next__ for it in iterables)
- while num_active:
- try:
- for next in nexts:
- yield next()
- except StopIteration:
- # Remove the iterator we just exhausted from the cycle.
- num_active -= 1
- nexts = cycle(islice(nexts, num_active))
+ # Algorithm credited to George Sakkis
+ iterators = map(iter, iterables)
+ for num_active in range(len(iterables), 0, -1):
+ iterators = cycle(islice(iterators, num_active))
+ yield from map(next, iterators)
def partition(predicate, iterable):
"""Partition entries into false entries and true entries.
@@ -997,10 +991,10 @@ The following recipes have a more mathematical flavor:
s = list(iterable)
return chain.from_iterable(combinations(s, r) for r in range(len(s)+1))
- def sum_of_squares(it):
+ def sum_of_squares(iterable):
"Add up the squares of the input values."
# sum_of_squares([10, 20, 30]) --> 1400
- return math.sumprod(*tee(it))
+ return math.sumprod(*tee(iterable))
def reshape(matrix, cols):
"Reshape a 2-D matrix to have a given number of columns."
@@ -1570,6 +1564,9 @@ The following recipes have a more mathematical flavor:
>>> list(roundrobin('abc', 'd', 'ef'))
['a', 'd', 'e', 'b', 'f', 'c']
+ >>> ranges = [range(5, 1000), range(4, 3000), range(0), range(3, 2000),
range(2, 5000), range(1, 3500)]
+ >>> collections.Counter(roundrobin(ranges)) == collections.Counter(ranges)
+ True
>>> def is_odd(x):
... return x % 2 == 1
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