Get unique values in List of Lists in python

Question

I want to create a list (or set) of all unique values appearing in a list of lists in python. I have something like this:

aList=[['a','b'], ['a', 'b','c'], ['a']] 

and i would like the following:

unique_values=['a','b','c'] 

I know that for a list of strings you can just use set(aList), but I can't figure how to solve this in a list of lists, since set(aList) gets me the error message

unhashable type: 'list' 

How can i solve it?

Answer 1

array = [['a','b'], ['a', 'b','c'], ['a']] result = {x for l in array for x in l} 

Answer 2

You can use itertools's chain to flatten your array and then call set on it:

from itertools import chain  array = [['a','b'], ['a', 'b','c'], ['a']] print set(chain(*array)) 

If you are expecting a list object:

print list(set(chain(*array)))