What makes something iterable in python

Question

What makes something iterable in Python? ie. can loop over it with for

Is it possible for me to create an iterable class in Python? If so, how?

Answer 1

To make a class iterable, write an __iter__() method that returns an iterator:

class MyList(object):
    def __init__(self):
        self.list = [42, 3.1415, "Hello World!"]
    def __iter__(self):
        return iter(self.list)

m = MyList()
for x in m:
    print(x)

prints

42
3.1415
Hello World!

The example uses a list iterator, but you could also write your own iterator by either making __iter__() a generator or by returning an instance of an iterator class that defines a __next__() method.