(:source lang=python:)

""" Iterators in python """

1. Many kinds of python objects can be iterated over using the for loop:
2. lists

for element in [1, 2, 3]:

    print element

1. strings

for char in "123":

    print char

1. files

for line in open("myfile.txt"):

    print line

1. Behind the scenes, the for statement calls iter() on the object.
2. this returns an iterator object - an object that has a next() method
3. which returns the next element in the sequence of elements.
4. When there are no more elements, next() raises a StopIteration exception
5. which tells the for loop to terminate.

s = 'abc' it = iter(s) it.next() it.next() it.next()

1. the next one will raise an exception:

it.next()

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