# Revision history [back]

As usual, Éric is right but delphic (pythic ?)... Try this

L=[]
S=set(L)
s=set(u)
if s not in S:
L.extend(u) ## Maybe L.extend(copy(u)) if sharing structures may be a problem later...
L


At the end of execution, L should contain lists differing by at least one element.