Flatten nested data structure in python 3

flatten.py

from collections import Iterable

def flatten(items):
    for item in items:
        if isinstance(item, Iterable):
            yield from flatten(item)
        else:
            yield item

nested = [1, 3, [3, [4, 5, [6]]]]
print(list(flatten(nested)))

[1, 3, 3, 4, 5, 6]

Python 2 version

In [49]: x
Out[49]: [[1, 2, [3]], 4]

In [50]: def flatten(items):
    for item in items:
        if isinstance(item, Iterable):
            for subitem in flatten(item): yield subitem
        else:
            yield item
   ....:

In [51]: list(flatten(x))
Out[51]: [1, 2, 3, 4]

   ....: