I run the following code and got wrong message, but I still want to make [1,2],[4,3] and [6,9] to be keys of the dictionary or change the style a little bit. How to do that? Thanks! >>> p=[[1,2],[4,3],[6,9]] >>> n=dict([(x,[]) for x in p]) Traceback (most recent call last): File "<interactive input>", line 1, in ? TypeError: list objects are unhashable >>>