The Python Apprentice

An example of the iteration protocols

As usual, a demonstration at the Python REPL will help all of these concepts crystallize into something you can work with. We start with a list of the names of the seasons as our iterable object:

>>> iterable = ['Spring', 'Summer', 'Autumn', 'Winter']

We then ask our iterable object to give us an iterator using the iter() built-in:

>>> iterator = iter(iterable)

Next we request a value from the iterator object using the next() built-in:

>>> next(iterator)'Spring'

Each call to next() moves the iterator through the sequence:

>>> next(iterator)'Summer'>>> next(iterator)'Autumn'>>> next(iterator)'Winter'

But what happens when we reach the end?

>>> next(iterator)Traceback (most recent call last): File "<stdin>", ...