Question

example #1:

class Person(object):
    pass

example #2:

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.

Answer 1

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.