On May 18, 11:22 am, timh <zutes...@gmail.com> wrote: > Hi > > I am trying to understand something about how the 'in' operator (as in > the following expression) > > if 'aa' in x: > do_something() > > When trying to implement in support on a class it appears that if > __contains__ doesn't exist > in falls back to calling __getitem__ > > However strange things happen to the name passed to __getitem__ in the > following example (and in fact in all varients I have triend the name/ > key passed to __getitem__ is always the integer 0 > > For instance > > Python 2.6.2 (release26-maint, Apr 19 2009, 01:56:41) > [GCC 4.3.3] on linux2 > Type "help", "copyright", "credits" or "license" for more information.>>> > class xx(object): > > ... def __getitem__(self,name): > ... raise KeyError(name) > ...>>> aa = xx() > >>> aa['kk'] > > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > File "<stdin>", line 3, in __getitem__ > KeyError: 'kk'>>> 'kk' in aa > > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > File "<stdin>", line 3, in __getitem__ > KeyError: 0 > > I am running on ubuntu, and this happens to 2.5.4 as well. I must say > I am surprised and > am at a loss as to what is actually going on. > > Can anyone enlighten me (or should I go and read some 'c' code ;-) > > Rgds > > Tim
See http://docs.python.org/library/functions.html#iter, that ought to clear it up. Thanks, Jeff mcjeff.blogspot.com -- http://mail.python.org/mailman/listinfo/python-list
