There's always reduce (being deprecated to functools):
>>> x = [ [ 'a', 'b'], ['c'] ]
>>> for el in reduce(lambda a,b: a+b, x, []):
... print el
...
__main__:1: DeprecationWarning: reduce() not supported in 3.x; use functools.reduce()
a
b
c
>>> import functools
>>> for el in functools.reduce(lambda a,b: a+b, x, []):
... print el
...
a
b
c
>>>
Unfortunately the plus operator for list concatenation can't be used as a function -- or fortunate, if you prefer lambdas to be ugly for improved visibility.
