Hello,
            how to find the list element that whether it is on other lists or not?
I know  by the  loop method (found= True). If you know better way please let me know. Thanks.
L1 = [1,2,3,4,5]
L2=[2,3,6]
L3=[1,6,8] 
L4 = [3,10]

result: 
1: L1,L3
2:  L1,L2
3: L1,L2,L4
6: L2,L3

not sure if this is the best way to do it:

load the elements to python disctionary ( that would be O(n) operation)
for each element in array, check if it exists in the disctionary , that would be another O(n) operation because hash lookup is O(1)