1 #!/usr/bin/env python
   2 # http://docs.python.org/tutorial/classes.html#iterators
   3 
   4 s = 'abc'
   5 it = iter(s)
   6 it.next()
   7 it.next()
   8 it.next()
   9 it.next()
  10 
  11 class Reverse:
  12     "Iterator for looping over a sequence backwards"
  13     def __init__(self, data):
  14         self.data = data
  15         self.index = len(data)
  16     def __iter__(self):
  17         return self
  18     def next(self):
  19         if self.index == 0:
  20             raise StopIteration
  21         self.index = self.index - 1
  22         return self.data[self.index]
  23 
  24 rev = Reverse('spam')
  25 for char in rev:
  26     print char