Python Iterators - thelastmile/FreeCodeCamp GitHub Wiki
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.
TODO: Clarify what iteration means and what iterators can be used for.
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Objects can implement a
__iter__()method that returns an iterator object to support iteration. -
Iterator objects must implement:
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__iter__(): returns the iterator object. -
__next__(): returns the next object of the container.
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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: