On 2 ene, 14:21, Ulrich Eckhardt <dooms...@knuut.de> wrote: > vsoler wrote: > > class stepper: > > def __getitem__(self, i): > > return self.data[i] > > > X=stepper() > > X.data="Spam" > > for item in X: > > print item, > > > ... what I get is S p a m which seems logical to me since the > > loop stops after the 4th character. > > I think you're mistaking the cause and effect here, see below. > > > class stepper: > > def __getitem__(self, i): > > return i > > > X=stepper() > > X.data="Spam" > > for item in X: > > print item, > > > ... what I get is an endless loop, starting at zero: 0 1 2 3 4 5 6 > > 7 8 9 10 11 and so on. > > > My question is: why does this second script not stop after printing > > number 3? what made the first one stop while the second one will not? > > First thing to observe in the second case is that X's data field is not used > anywhere. The field is set and then not used any further. In particular, it > is not used to somehow get the length of the sequence to return. > > Now, "spam"[4] will raise an IndexError, thus terminating the iteration. The > second implementation which only returns the index never will do that, so > the iteration never stops. > > Uli
It's clear, I now understand. Thank you -- http://mail.python.org/mailman/listinfo/python-list
