class Person(object):
pass
class Person:
pass
What does the object declaration do? Should you use it? I have a bunch of programs with both of them and don't know the difference it is making. If anyone can explain this concept please.
In Python2, declaring object as the base class makes the class a new-style class. Otherwise, it is a "classic" class. Among the differences are that
Properties only work with new-style classes
new-style classes have the mro method
new-style classes have many attributes that classic classes lack
In [288]: class Foo: pass
In [289]: dir(Foo)
Out[289]: ['__doc__', '__module__']
In [290]: class Bar(object): pass
In [291]: dir(Bar)
Out[291]: ['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__']
Classic classes are retained in Python2 only for backwards compatibility. All custom classes you define should be made new-style.
In Python3, all classes are new-style, so it need not be explicitly declared there.
a = oldstyle(); a.__add__ = lambda *args: 'changed' will work but the equivalent with a newstyle object won't. Maybe once or twice I've wished this would work without creating a new class instead, but that's it, and mostly it was a sign my structures needed rethinking.In Python 2, the object makes it a "new-style class". The details of what this means aren't too important, but the bottom line is you should always use it or some things might not work right.
In Python 3, everything is always a new-style class, so you don't need to use object there.
