Is it necessary or useful to inherit from Python's object in Python 3.x?

Question

In older Python versions when you create a class, it can inherit from object which is as far I understand a special built-in Python element that allows your class to be a new-style class.

What about newer versions (> 3.0 and 2.6)? I googled about the object class but I get so many results (for obvious reasons).

Asked By: thomas

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Answer 1

You don’t need to inherit from object to have new style in python 3. All classes are new-style.

Answered By: SilentGhost

Answer 2

I realise that this is an old question, but it is worth noting that even in python 3 these two things are not quite the same thing.

If you explicitly inherit from object, what you are actually doing is inheriting from builtins.object regardless of what that points to at the time.

Therefore, I could have some (very wacky) module which overrides object for some reason. We’ll call this first module “newobj.py”:

import builtins

old_object = builtins.object  # otherwise cyclic dependencies

class new_object(old_object):

    def __init__(self, *args, **kwargs):
        super(new_object, self).__init__(*args, **kwargs)
        self.greeting = "Hello World!" 

builtins.object = new_object  #overrides the default object

Then in some other file (“klasses.py”):

class Greeter(object):
    pass

class NonGreeter:
    pass

Then in a third file (which we can actually run):

import newobj, klasses  # This order matters!

greeter = klasses.Greeter()
print(greeter.greeting)  # prints the greeting in the new __init__

non_greeter = klasses.NonGreeter()
print(non_greeter.greeting) # throws an attribute error

So you can see that, in the case where it is explicitly inheriting from object, we get a different behaviour than where you allow the implicit inheritance.

Answered By: Philip Adler

Is it necessary or useful to inherit from Python's object in Python 3.x?

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