Iterators in for Loops

>>> cities = ["Paris","Berlin","London"]

>>> for city in cities:

... print("city: " + city)

...

city: Paris

city: Berlin

city: London

Whats happening?

• The built-in function iter with iter(cities), which calls __iter__ of the list class. The return value – a „list_iterator” - is stored in a variable, e.g. iter_x.
• After each loop the next function ist called with iter_x as an argument and the return value of this call is assigned to the variable iter_x.
• The loop will be repeated until next(iter_x) raises the exception StopIteration.