mirror of https://github.com/python/cpython.git
Improve itertools docs with clearer examples of pure python equivalent code.
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@ -1367,10 +1367,10 @@ are always available. They are listed here in alphabetical order.
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def zip(*iterables):
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# zip('ABCD', 'xy') --> Ax By
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sentinel = object()
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iterables = [iter(it) for it in iterables]
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while iterables:
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iterators = [iter(it) for it in iterables]
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while iterators:
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result = []
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for it in iterables:
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for it in iterators:
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elem = next(it, sentinel)
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if elem is sentinel:
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return
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@ -557,16 +557,25 @@ loops that truncate the stream.
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iterables are of uneven length, missing values are filled-in with *fillvalue*.
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Iteration continues until the longest iterable is exhausted. Equivalent to::
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def zip_longest(*args, fillvalue=None):
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class ZipExhausted(Exception):
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pass
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def zip_longest(*args, **kwds):
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# zip_longest('ABCD', 'xy', fillvalue='-') --> Ax By C- D-
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def sentinel(counter = ([fillvalue]*(len(args)-1)).pop):
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yield counter() # yields the fillvalue, or raises IndexError
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fillvalue = kwds.get('fillvalue')
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counter = len(args) - 1
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def sentinel():
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nonlocal counter
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if not counter:
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raise ZipExhausted
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counter -= 1
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yield fillvalue
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fillers = repeat(fillvalue)
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iters = [chain(it, sentinel(), fillers) for it in args]
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iterators = [chain(it, sentinel(), fillers) for it in args]
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try:
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for tup in zip(*iters):
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yield tup
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except IndexError:
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while iterators:
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yield tuple(map(next, iterators))
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except ZipExhausted:
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pass
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If one of the iterables is potentially infinite, then the :func:`zip_longest`
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