What is the fastest way to flatten arbitrarily nested lists in Python? [duplicate]

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Here’s a recursive approach that is string friendly:

nests = [1, 2, [3, 4, [5],['hi']], [6, [[[7, 'hello']]]]]

def flatten(container):
    for i in container:
        if isinstance(i, (list,tuple)):
            for j in flatten(i):
                yield j
        else:
            yield i

print list(flatten(nests))

returns:

[1, 2, 3, 4, 5, 'hi', 6, 7, 'hello']

Note, this doesn’t make any guarantees for speed or overhead use, but illustrates a recursive solution that hopefully will be helpful.

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