set of list of lists in python

Question

I am having a list of lists :

mat = [[1,2,3],[4,5,6],[1,2,3],[7,8,9],[4,5,6]]

and I want to convert into a set

Answer 1

Lists are mutable, therefore unhashable. Use tuples instead

In [114]: mat = [[1,2,3],[4,5,6],[1,2,3],[7,8,9],[4,5,6]]

In [115]: mat = [tuple(t) for t in mat]

In [116]: matset = set(mat)

In [117]: matset
Out[117]: {(1, 2, 3), (4, 5, 6), (7, 8, 9)}

In [118]: [list(t) for t in matset]
Out[118]: [[4, 5, 6], [7, 8, 9], [1, 2, 3]]