This Python Iterators lesson is for a beginner. Read the short notes, run each example, then change one name or number and run it again.
An iterator remembers where it is in a stream of values. iter builds one. next asks for the following value.
A for loop calls those steps for you. You write next yourself when you want one value at a time.
Example 1: Start here
Asking past the end raises StopIteration.
names = iter(["Meera", "Arun"]) # a walker that gives one value at a time
print(next(names))
print(next(names))
Example 2: Next pulls one item
iter starts the iterator. next returns one item and moves forward.
skills = iter(["Python", "SQL"]) # a walker that gives one value at a time
print(next(skills))
print(next(skills))
Example 3: A for loop uses the iterator
A for loop calls next for you and stops at the end.
for skill in ["Python", "SQL"]: # repeat the indented lines once per value
print(skill)
Example 4: A default at the end
The second argument of next is returned when there is nothing left.
skills = iter(["Python"]) # a walker that gives one value at a time
print(next(skills, "done"))
print(next(skills, "done"))
Asking past the end raises StopIteration.
