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Two of Python's built-in functions, :func:`map` and :func:`filter` duplicate the
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features of generator expressions:
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``map(f, iterA, iterB, ...)`` returns an iterator over the sequence
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``map(f, iterA, iterB, ...)`` returns an iterator over the sequence
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``f(iterA[0], iterB[0]), f(iterA[1], iterB[1]), f(iterA[2], iterB[2]), ...``.
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>>> [upper(s) for s in ['sentence', 'fragment']]
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``filter(predicate, iter)`` returns an iterator over all the sequence elements
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that meet a certain condition, and is similarly duplicated by list