Function to remove elements from a list not working (corrected)

[Girish Sahani]

Hi,
 I am trying to modify a list of pairs (l4) by removing those
pairs which are not present in a third list called pairList.
 The following is a simplified part of the routine i have written. However
it does not give the correct output. Please help!
 Its possible i have made a trivial mistke since i am a newbie.

def getl5():
    l5 = []
    pairList = [[1,2],[3,4],[3,5],[3,6],[9,7],[8,9],[8,7],[7,9],[11,10]]
    l4 = [[4,2],[4,7],[4,10],[4,12],[9,2],[9,7],[9,10],[9,12],[11,2],[11,7]]
    for pair in l4:
        if pair not in pairList:
            l4.remove(pair)
    print "l4 is",l4

The output given is:
l4 is [[4, 7], [4, 12], [9, 7], [9, 12], [11, 7]]