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copied!<p>This version of <code>flatten</code> avoids python's recursion limit (and thus works with arbitrarily deep, nested iterables). It is a generator which can handle strings and arbitrary iterables (even infinite ones).</p> <pre><code>import itertools as IT import collections def flatten(iterable, ltypes=collections.Iterable): remainder = iter(iterable) while True: first = next(remainder) if isinstance(first, ltypes) and not isinstance(first, basestring): remainder = IT.chain(first, remainder) else: yield first </code></pre> <p>Here are some examples demonstrating its use:</p> <pre><code>print(list(IT.islice(flatten(IT.repeat(1)),10))) # [1, 1, 1, 1, 1, 1, 1, 1, 1, 1] print(list(IT.islice(flatten(IT.chain(IT.repeat(2,3), {10,20,30}, 'foo bar'.split(), IT.repeat(1),)),10))) # [2, 2, 2, 10, 20, 30, 'foo', 'bar', 1, 1] print(list(flatten([[1,2,[3,4]]]))) # [1, 2, 3, 4] seq = ([[chr(i),chr(i-32)] for i in xrange(ord('a'), ord('z')+1)] + range(0,9)) print(list(flatten(seq))) # ['a', 'A', 'b', 'B', 'c', 'C', 'd', 'D', 'e', 'E', 'f', 'F', 'g', 'G', 'h', 'H', # 'i', 'I', 'j', 'J', 'k', 'K', 'l', 'L', 'm', 'M', 'n', 'N', 'o', 'O', 'p', 'P', # 'q', 'Q', 'r', 'R', 's', 'S', 't', 'T', 'u', 'U', 'v', 'V', 'w', 'W', 'x', 'X', # 'y', 'Y', 'z', 'Z', 0, 1, 2, 3, 4, 5, 6, 7, 8] </code></pre> <p>Although <code>flatten</code> can handle infinite generators, it can not handle infinite nesting:</p> <pre><code>def infinitely_nested(): while True: yield IT.chain(infinitely_nested(), IT.repeat(1)) print(list(IT.islice(flatten(infinitely_nested()), 10))) # hangs </code></pre>

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