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.
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 :
<str_iterator object at 0x102e196a0>
4343305888
4343305888
a
b
c
---------------------------------------------------------------------------
StopIteration Traceback (most recent call last)
<ipython-input-1-d466eea8c1b0> in <module>()
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: