Python merge all child list into parent list and remove duplicates

Question

I have a huge list of lists. I want to Merge all child lists to parent list and remove duplicates item from parent list after merge.

What is the optimized wa

Answer 1

Use set

x = [['a', 'b', 'c', 2, 4], ['x', 1, 2, 3, 'z'], ['z', 'b', 'y', 'a' 'x']]
>>> list(set([item for sublist in x for item in sublist]))
[1, 2, 3, 4, 'z', 'ax', 'a', 'b', 'c', 'x', 'y']