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Flatten an irregular list of lists in Python

Let’s say I would like to flatten an irregular list of lists.

lst = [[[1, 2, 3], [4, 5]], 6]

First approach is by using collections.Iterable

import collections

def flatten(x):
    if isinstance(x, collections.Iterable):
        return [a for i in x for a in flatten(i)]
        return [x]

where x is the irregular list of lists.


Second approach is a recursive flatten approach which handles both tuples and lists

flatten = lambda *n: (e for a in n
    for e in (flatten(*a) if isinstance(a, (tuple, list)) else (a,)))
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