An expression like this creates a list of integers: >>> [0] * 2 [0, 0]
But an expression like this creates list of references to the list named `foo': >>> foo = [0, 0] >>> baz = [foo] * 2 [foo, foo] So, setting baz[0][0] = 1, is really setting foo[0] = 1. There is only one instance of foo, but you have multiple references. Try a list comprehension to get the result you want: >>> foo = [[0 for ii in range(2)] for jj in range(2)] -- http://mail.python.org/mailman/listinfo/python-list
