python generators and iterators

#! /usr/bin/env python 
# -*- coding:utf-8 -*- 

def xrange(n): 
    num = 0 
    while True: 
        if num > n: 
            return 
        print(num) 
        yield num 
        num += 1 

obj = xrange(5)# obj is that the generator only has the ability to generate #Iterator 
: with access ability, no random access, only from the beginning to the end 
# Can't go back, which is convenient for looping relatively large data sets 
# n1 = obj.__next__() 
# n2 = obj.__next__() 
# n3 = obj.__next__() 

for n in xrange(10): 
    print(n)