How can an instance be iterated over?

Question

In datatstructures.py, there is a method values():

def values(self):
    """Iterate over all values."""
    for item in self:
        yield item[0]

self is an instance of the class; how can it be iterated over?

Answer 1

Simple, it has to implement __iter__ method, e.g.

class Test:
    def __iter__(self):
        yield 1
        yield 2

>>> instance = Test()
>>> for val in instance:
...     print val
...
1
2