Hi.. I have a problem.. list1=[11, 223, 334, 4223...] 1 million element list2=[22,223,4223,2355...] 500.000 element I want to difference list1 to list2 but order very importent.. My result must be: list3=[11,334,...] I do this use FOR easly but the speed very imported for me. I want to the fastest method please help me. I'm sorry my bad english. King regards..