How do I unnest a tuple with mixed types?

Question

I'm trying to flatten a tuple with mixed types into a list. The following function does not produce the desired output:

a = (1, 2, 3, ['first', 'second'])
def flatten(l): 
return flatten(l[0]) + (flatten(l[1:]) if len(l) > 1 else []) if type(l) is list else [l]

>>> flatten(a)
[(1, 2, 3, ['first', 'second'])]
>>> flatten(flatten(a))
[(1, 2, 3, ['first', 'second'])]
>>> [flatten(item) for item in a]
[[1], [2], [3], ['first', 'second']]

the output should be:

>>> [1, 2, 3, 'first', 'second']

Either that or http://stackoverflow.com/questions/406121/flattening-a-shallow-list-in-python — Morgan Thrapp, Jun 27 '16 at 15:26
Did *none* of the existing questions regarding flattening nested sequences help you? There are quite a few... — jonrsharpe, Jun 27 '16 at 15:26
`if type(l) is list` obviously won't work correctly if the input is a tuple, you may want to check `isinstance(l, (list,tuple))` instead. — Tadhg McDonald-Jensen, Jun 27 '16 at 15:35

score 0 · Accepted Answer · answered Jun 27 '16 at 15:39

def flatten(l):
    if isinstance(l, (list,tuple)):
        if len(l) > 1:
            return [l[0]] + flatten(l[1:])
        else:
            return l[0]
    else:
        return [l]

a = (1, 2, 3, ['first', 'second'])

print(flatten(a))

[1, 2, 3, 'first', 'second']

How do I unnest a tuple with mixed types?

1 Answers1