On 29/07/11 21:36, Billy Mays wrote: > Is xrange not a generator? I know it doesn't return a tuple or list, > so what exactly is it? Y doesn't ever complete, but x does. > > x = (i for i in range(10)) > y = xrange(10) > > print "===X===" > while True: > for i in x: > print i > break > else: > break > > print "===Y===" > while True: > for i in y: > print i > break > else: > break
Every for loop calls gets a new iterator from the object you're iterating over. (__iter__) -- Apparently, xrange is implemented in such a way (as are lists) that you can iterate over the object many times, while each generator object (and how could it be otherwise can only be iterated over once. What is xrange(foo)? It is an object that supports list-like indices, the iterator protocol, and probably a few other things that you will find in the stdlib docs. Generators also support the iterator protocol, but that's about as far as the similarity goes (in general) - Thomas -- http://mail.python.org/mailman/listinfo/python-list