def remove_dups(L1, L2):
i = 0
while i < len(L1):
if L1[i] in L2:
L1.remove(L1[i])
else:
i += 1
L1 = [1, 2, 3, 4]
L2 = [1, 2, 5, 6]
remove_dups(L1, L2)
print(L1)
#https://pt.stackoverflow.com/q/288232/101
ZGVmIHJlbW92ZV9kdXBzKEwxLCBMMik6CiAgICBpID0gMAogICAgd2hpbGUgaSA8IGxlbihMMSk6CiAgICAgICAgaWYgTDFbaV0gaW4gTDI6CiAgICAgICAgICAgIEwxLnJlbW92ZShMMVtpXSkKICAgICAgICBlbHNlOgogICAgICAgICAgICBpICs9IDEKCkwxID0gWzEsIDIsIDMsIDRdCkwyID0gWzEsIDIsIDUsIDZdCnJlbW92ZV9kdXBzKEwxLCBMMikKcHJpbnQoTDEpCgojaHR0cHM6Ly9wdC5zdGFja292ZXJmbG93LmNvbS9xLzI4ODIzMi8xMDE=