Peter Mott wrote: > If I use concatenation + instead of multiplication * then I get the > result that Jiri expected: > > >>> L = [[]] + [[]] > >>> L[1].append(1) > >>> L > [[], [1]] > > With * both elements are changed: > > >>> L = [[]] * 2 > >>> L[1].append(1) > >>> L > [[1], [1]] > > Alex Martelli says in his excellent Nutshell book that + is > concatenation and that "n*S is the concatenation of n copies of S". But > it seems not so. Surely, from a logical point of view, S + S should be > the same as S * 2? > What you did was not S+S. You did S+T, i.e. you added two distinct lists. Try it again adding the same list and you will see that both addition and multplication do work the same:
>>> S = [[]] >>> L = S + S >>> L[1].append(1) >>> L [[1], [1]] >>> S = [[]] >>> L = 2*S >>> L[1].append(1) >>> L [[1], [1]] -- http://mail.python.org/mailman/listinfo/python-list
