Don't generate list of python mutables using "*" operator

gistfile1.pytb

>>> m = [[]] * 10
>>> m
[[], [], [], [], [], [], [], [], [], []]
>>> #everything seems to be OK
... 
>>> m[0].append(10)
>>> m
[[10], [10], [10], [10], [10], [10], [10], [10], [10], [10]]
>>> #shit!
... 
>>> m = [set()] * 10
>>> m
[set([]), set([]), set([]), set([]), set([]), set([]), set([]), set([]), set([]), set([])]
>>> m[0].add(10)
>>> m
[set([10]), set([10]), set([10]), set([10]), set([10]), set([10]), set([10]), set([10]), set([10]), set([10])]
>>> #you already knew that
... 
>>> 
>>> #That's how we need to to this:
... 
>>> m = [[] for i in range(10)]
>>> m
[[], [], [], [], [], [], [], [], [], []]
>>> m[0].append(10)
>>> m
[[10], [], [], [], [], [], [], [], [], []]