What is the purpose of subclassing the class "object" in Python?

In short, it sets free magical ponies.

In long, Python 2.2 and earlier used "old style classes". They were a particular implementation of classes, and they had a few limitations (for example, you couldn't subclass builtin types). The fix for this was to create a new style of class. But, doing this would involve some backwards-incompatible changes. So, to make sure that code which is written for old style classes will still work, the object class was created to act as a superclass for all new-style classes.So, in Python 2.X, class Foo: pass will create an old-style class and class Foo(object): pass will create a new style class.

In longer, see Guido's Unifying types and classes in Python 2.2.

And, in general, it's a good idea to get into the habit of making all your classes new-style, because some things (the @property decorator is one that comes to mind) won't work with old-style classes.

Short answer: subclassing object effectively makes it a new-style class (note that this is unnecessary since automatic in Python 3.x)

For the difference between new style classes and old style classes: see this stackoverflow question. For the complete story: see this nice writeup on Python Types and Objects.

It has to do with the "new-style" of classes. You can read more about it here: http://docs.python.org/tutorial/classes.html#multiple-inheritance and also here: http://docs.python.org/reference/datamodel.html#new-style-and-classic-classes

Using new-style classes will allow you to use "Python's newer, versatile features like __slots__, descriptors, properties, and __getattribute__()."