Subtracting two lists in Python

Question

In Python, How can one subtract two non-unique, unordered lists? Say we have a = [0,1,2,1,0] and b = [0, 1, 1] I\'d like to do something like

Answer 1

list(set([x for x in a if x not in b]))

• Leaves a and b untouched.
• Is a unique set of "a - b".
• Done.