Difference between two lists of lists in Python

Question

I have two lists of lists:

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

I would like to get a set difference between them - expected outcome:

c = a - b = [[4,5,6],[7,8,9]].

I tried set() and set.difference() but it seems not to be able to compare lists.

Answer 1

You can iterate through one and check if it's in the other.

[numbers for numbers in a if numbers not in b]