On Sun, Aug 9, 2015 at 9:00 PM, Pierre Quentel <pierre.quen...@gmail.com> wrote: >> The trap you're seeing here is that iterating over an iterator always >> consumes it, but mentally, you're expecting this to be iterating over >> a new instance of the same sequence. > > No, I just tried to apply what I read in the docs : > > 1. I have y = A(10) which is an instance of a class which does not define > __contains__ but does define __iter__ > > 2. The value z = 0 is produced while iterating over y. > > 3. The sentence "x in y is true if some value z with x == z is produced while > iterating over y" lead me to think that "0 in y" would be true.
You're almost right. The significance here is that once you've partially iterated over y, the value z will not be produced while iterating over y - so *at that point in time*, y does not contain z. Iterators (non-infinite ones, at least) shrink over time, so the set of objects they contain will shrink. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
