Flattening lists

[Rhamphoryncus]

On Feb 6, 10:21 pm, rdmur... at bitdance.com wrote:
> Quoth Mensanator <mensana... at aol.com>:
> > def flatten(listOfLists):
> >     return list(chain.from_iterable(listOfLists))
>
>     Python 2.6.1 (r261:67515, Jan  7 2009, 17:09:13)
>     [GCC 4.3.2] on linux2
>     Type "help", "copyright", "credits" or "license" for more information.
>     >>> from itertools import chain
>     >>> list(chain.from_iterable([1, 2, [3, 4]]))
>     Traceback (most recent call last):
>       File "<stdin>", line 1, in <module>
>     TypeError: 'int' object is not iterable
>     >>> list(chain(*[1, 2, [3, 4]]))
>     Traceback (most recent call last):
>       File "<stdin>", line 1, in <module>
>     TypeError: 'int' object is not iterable
>     >>> list(chain.from_iterable(['abcd', 'efg', [3, 4]]))
>     ['a', 'b', 'c', 'd', 'e', 'f', 'g', 3, 4]

What usecase do you have for such inconsistently structured data?

If I'm building a tree I use my own type for the nodes, keeping them
purely internal, so I can always use isinstance without worrying about
getting something inconvenient passed in.