An iterator is nothing more than a container object that implements the iterator protocol. It is based on two methods:
Iterators can be created with a sequence using the iter built-in function, for example:
>>> i = iter('abc')
>>> i.next()
'a'
>>> i.next()
'b'
>>> i.next()
'c'
>>> i.next()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
StopIterationWhen the sequence is exhausted, a StopIteration exception is raised. It makes iterators compatible with loops since they catch this exception to stop cycling. To create a custom iterator, a class with a next method can be written, as long as it provides the special method __iter__ that returns an instance of the iterator:
>>> class MyIterator(object): ... def __init__(self, step): ... self.step = step ... def next(self...