Remove all the elements that occur in one list from another

Question

Let\'s say I have two lists, l1 and l2. I want to perform l1 - l2, which returns all elements of l1 not in l2

Answer 1

Use the Python set type. That would be the most Pythonic. :)

Also, since it's native, it should be the most optimized method too.

See:

http://docs.python.org/library/stdtypes.html#set

http://docs.python.org/library/sets.htm (for older python)

# Using Python 2.7 set literal format.
# Otherwise, use: l1 = set([1,2,6,8])
#
l1 = {1,2,6,8}
l2 = {2,3,5,8}
l3 = l1 - l2