17:04 August 29, 2013

i knew there was a trick:

>>> sum([['a'], ['b'], ['c']])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'int' and 'list'
>>> sum([['a'], ['b'], ['c']], [])
['a', 'b', 'c']