---
title: Python Iterators
---
Python supports a concept of iteration over containers. This is implemented using two distinct methods; these are used to allow user-defined classes to support iteration.
Python Docs - Iterator Types
Iteration is the process of programatically repeating a step a given number of times. A programmer can make use of iteration to perform the same operation on every item in a collection of data, for example printing out every item in a list.
* Objects can implement a `__iter__()` method that returns an iterator object to support iteration.
* Iterator objects must implement:
* `__iter__()`: returns the iterator object.
* `__next__()`: returns the next object of the container.
iterator_object = 'abc'.__iter__()
print(iterator_object)
print(id(iterator_object))
print(id(iterator_object.__iter__())) # Returns the iterator itself.
print(iterator_object.__next__()) # Returns 1st object and advances iterator.
print(iterator_object.__next__()) # Returns 2nd object and advances iterator.
print(iterator_object.__next__()) # Returns 3rd object and advances iterator.
print(iterator_object.__next__()) # Raises StopIteration Exception.
Output :
4343305888
4343305888
a
b
c
---------------------------------------------------------------------------
StopIteration Traceback (most recent call last)
in ()
6 print(iterator_object.__next__()) # Returns 2nd object and advances iterator.
7 print(iterator_object.__next__()) # Returns 3rd object and advances iterator.
----> 8 print(iterator_object.__next__()) # Raises StopIteration Exception.
StopIteration: