iterates

iter1.py

a = [1,2,3]
i = iter(a)
i.next()

iter2.py

# iterator
for i in [1,2,3]:
  print i*i

# generator
def square(li):
  for i in xrange(1, li):
    yield i*i

for i in square(3):
  print i

'''
actually this is not a good example because code for generator 
is much more than that of iterator. 
but ...
'''