[issue8376] Tutorial offers dangerous advice about iterators: “__iter__() can just return self”

[loic rowe]

loic rowe added the comment:

A new proposal is to add at the end of the paragraph on the iterator those point:
"""
As you should have noticed this Reverse let you iterate over the data only once::

   >>> rev = Reverse('spam')
   >>> for char in rev:
   ...     print(char)
   ...
   m
   a
   p
   s
   >>> for char in rev:
   ...     print(char)
   ...
   >>>

So now let's complete our example to have a container that allow you to iterate over his items backwards::

  class ReverseList(object):
       "Container that lets you iterate over the items backwards"
       def __init__(self, data):
           self.data = data
       def __iter__(self):
           return ReverseIterator(self.data)

   class ReverseIterator(object):
       "Iterator for looping over a sequence backwards"
       def __init__(self, data):
           self.data = data
           self.index = len(data)
       def __iter__(self):
           return self
       def next(self):
           if self.index == 0:
               raise StopIteration
           self.index = self.index - 1
           return self.data[self.index]

   >>> rev = ReverseList([1,2,3])
   >>> for char in rev:
   ...     print (char)
   ...
   3
   2
   1
   >>> for char in rev:
   ...     print (char)
   ...
   3
   2
   1
"""

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue8376>
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