"""
 generator.py
 a demo of python generator

 $ python generator.py
 0
 1
 2
 3
 4 

"""

def count_to_n(n):
   i = 0
   while True:
      if i < n:
         yield i
         i = i + 1
      else:
         return

for i in count_to_n(5):
   print(i)