Question

Is it possible to add dict functionality to user created classes?

ie:

class Foo(object):
    def __init__(self, x, y):
       self.x
       self.y
    def __dict__(self):
       return {'x': self.x, 'y': self.y}

f = Foo()
dict(f) <-- throws TypeError: iteration over non-sequence

Answer 1

The dict constructor expects either a mapping or an iterable of key/value pairs as a parameter, so your class needs to either implement the mapping protocol or be iterable.

Here’s an example how to got about the latter approach:

class Foo(object):
    def __init__(self, x, y):
       self.x = x
       self.y = y
    def __iter__(self):
       return vars(self).iteritems()

Example usage:

>>> dict(Foo(2, 3))
{'x': 2, 'y': 3}

I don’t know how useful this is, though. You could just do

>>> vars(Foo(2, 3))
{'x': 2, 'y': 3}

which would work without implementing __iter__() on your class.