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