Question

Perhaps I’m overlooking something simple, but I would like to cast an instance of a custom class as a dictionary in python (for the sake of readability), but haven’t got an inkling as to how. To explain in pseudocode, I would like to be able to do this:

class A:
   # class things...

a = A()
b = dict(a)

where I have defined what b will be within A. Is this possible?

Answer 1

If you define __iter__, it’ll Just Work(tm):

class A(object):
    def __init__(self, a, b):
        self.a = a
        self.b = b
    def __iter__(self):
        return vars(self).iteritems()

gives

>>> A(2,3)
<__main__.A object at 0x101ea70d0>
>>> dict(A(2,3))
{'a': 2, 'b': 3}

and you can return or yield whatever you like. That said, I second the suggestion in the comments that you should really just implement a .to_dict() method instead, as often __iter__ is too useful for other purposes to waste on this one.