Python inheritance old style type in a new style class

Question

I'm using the csv.DictWriter class, and I want to inherit it:

class MyObj(csv.Dictwriter):
    ...

But this type is an old-style object. Can MyObj be a new-style class but still inherit from csv.DictWriter?

Answer 1

Yes, you only have to inherit from object, too:

class MyObj(object, csv.DictWriter):
    def __init__(self, f, *args, **kw):
        csv.DictWriter.__init__(self, f, *args, **kw)

Answer 2

As Daniel correctly states, you need to mixin object. However, one major point of using new-style classes is also using super, thus you should use

class MyObj(csv.DictWriter, object):
    def __init__(self, csvfile, mycustomargs, *args, **kwargs):
        super(MyOobj, self).__init__(csvfile, *args, **kwargs)
        ...

As mentioned elsewhere, object should be the last parent, otherwise object's default methods such as __str__ and __repr__ will override the other parent's implementation, which is certainly not what you wanted...