a = [1,2,3] b = [a,a,a] # Copy c = b d = b.copy() # b c d all point at the same object. if one of the them is changed, all of them are changed. from copy import deepcopy f = deepcopy(b) # python offers a function called deepcopy that allows to create a new object so that you can do anything with f while there is no influence on b.