Does Python have anonymous classes?

Question

I\'m wondering if Python has anything like the C# anonymous classes feature. To clarify, here\'s a sample C# snippet:

var foo = new { x = 1, y = 2 };
var bar          


        

Answer 1

1) See http://uszla.me.uk/space/blog/2008/11/06. You can create an anonymous object with slightly ugly syntax by using the type built-in function:

 anon_object_2 = type("", (), {})()

where the 3rd parameter is the dict that will contain the fields of your object.

 foo = type("", (), dict(y=1))()
 foo.y == 1

2) Another variation is proposed by Peter Norvig at http://norvig.com/python-iaq.html. It is also similar to the answer posted by Ken.

class Struct:
    def __init__(self, **entries): self.__dict__.update(entries)

>>> options = Struct(answer=42, linelen = 80, font='courier')
>>> options.answer
42

The benefit of this method is that you can implement equality by contents of the dict, which the first option doesn't have.

Answer 2

The pythonic way would be to use a dict:

>>> foo = dict(x=1, y=2)
>>> bar = dict(y=2, x=1)
>>> foo == bar
True

Meets all your requirements except that you still have to do foo['x'] instead of foo.x.

If that's a problem, you could easily define a class such as:

class Bunch(object):
    def __init__(self, **kwds):
        self.__dict__.update(kwds)

    def __eq__(self, other):
        return self.__dict__ == other.__dict__

Or, a nice and short one

class Bunch(dict):
    __getattr__, __setattr__ = dict.get, dict.__setitem__

(but note that this second one has problems as Alex points out in his comment!)