经典类与新式类、钻石继承(菱形继承)、多继承之“广度优先”“深度优先”

# 新式类：
class User(object):
    pass

class Sub(User):
    pass


# 在python3中所有的类都是新式类(默认继承object)
class Bar:
    pass

print(Bar.__bases__)    # (<class 'object'>,)

class Father1:
    x = 10

class Father2:
    x = 20

class Father3:
    x = 30

# 多继承的情况下：从左到右
class Sub(Father1, Father2, Father3):
    # 注意：__int__  不是  __init__
    def __init__(self):
        print(super().x)


obj = Sub()
print(Sub.mro())
# 子类和父类中都没有这个方法，但是object中有，所以从object中找到.__dir__
print(Sub.__dir__)

10
[<class '__main__.Sub'>, <class '__main__.Father1'>, <class '__main__.Father2'>, <class '__main__.Father3'>, <class 'object'>]
<method '__dir__' of 'object' objects>

class A(object):
    def test(self):
        print("from A")

class B(A):
    def test(self):
        print("from B")

class C(A):
    def test(self):
        print("from C")

class D(B):
    def test(self):
        print("from D")

class E(C):
    def test(self):
        print("from E")

class F(D, E):
    def test(self):
        print("from F")


print(F.mro())

[<class '__main__.F'>, <class '__main__.D'>, <class '__main__.B'>, <class '__main__.E'>, <class '__main__.C'>, <class '__main__.A'>, <class 'object'>]

class A(object):
    def test(self):
        print("from A")

class B(A):
    # def test(self):
        # print("from B")
    pass

class C(A):
    def test(self):
        print("from C")

class D(B):
    # def test(self):
    #     print("from D")
    pass

class E(C):
    def test(self):
        print("from E")

class F(D, E):
    # def test(self):
    #     print("from F")
    pass


obj = F()
print(obj.test())

from E