Why do Python classes inherit object classes

python class Be sure to inherit object Class? ？ Why? ？

Inherit object Class is a new class , No inheritance object Class is a classic class , stay Python 2.7 There will be differences between the new class and the classic class in terms of multiple inheritance ：

class A:
def foo(self):
print('called A.foo()')
class B(A):
pass
class C(A):
def foo(self):
print('called C.foo()')
class D(B, C):
pass
if __name__ == '__main__':
d = D()
d.foo()

B、C yes A Subclasses of ,D More inherited B、C Two classes , among C Rewrote A Medium foo() Method .

If A It's a classic class （ Code above ）, When calling D Instance foo() When the method is used ,Python According to Depth first The way to search foo() , The path is a B-A-C , Execution is A Medium foo() ;

If A It's new , When calling D Instance foo() When the method is used ,Python Will press Photo breadth first The way to search foo() , The path is a B-C-A , Execution is C Medium foo() . because D It's direct inheritance C Of , Logically speaking , perform C Medium foo() It is more reasonable , Therefore, the handling of multi inheritance by new classes is more logical .

stay Python 3.x The new classes in seem to be compatible with the classic classes , No matter what A Whether to inherit object class , D In the instance foo() It will be carried out C Medium foo() . But in Python 2.7 There is still a difference in , Therefore, the new class is recommended , Inheritance object class .

Reference resources :

1. https://www.zhihu.com/question/19754936
2. https://stackoverflow.com/questions/4015417/why-do-python-classes-inherit-object