The For-loops – iterating over series of items

Now that we have the tools to make some interesting data structures, we'll look
at Python's other type of loop construct, the for-loop. The for-loops in Python correspond to what are called for-each loops in many other programming languages. They request items one-by-one from a collection – or more strictly from an iterable series (but more of that later) – and assign them in turn to the a variable we specify. Let's create a list collection, and use a for-loop to iterate over it, remembering to indent the code within the for-loop by four spaces:

>>> cities = ["London", "New York", "Paris", "Oslo", "Helsinki"]
>>> for city in cities:
...     print(city)
...
London
New York
Paris
Oslo
Helsinki

So iterating over a list yields the items one...