On Apr 6, 11:16 pm, Helmut Jarausch <jarau... at skynet.be> wrote: > Hi, > > I must be blind but I don't see what's going wrong > with The reason is: > G=[[]]*2 is doing a "shallow copy" of the blank list. The corrected code is either: G = [[] for _ in xrange(2)] or G = [[], []] btw, this is a very frequently asked question