面向对象三大特性：封装、继承、多态

组合：一个类的对象是另一个类或对象的属性

继承：python可多继承

python3中默认继承object类

python3所有类都是新式类（默认继承object）

单继承中可以用super().xxx调用父类方法或属性

class A(object):
    name1 = 'A'
    def __init__(self):
        print('A is init')

    def f1(self):
        print('f1 in A')


class B(object):
    name2 = 'B'
    def __init__(self):
        print('B is init')

    def f2(self):
        print('f2 in B')


class C(A, B):
    name3 = 'C'
    def __init__(self):
        A.__init__(self)
        B.__init__(self)
        print('C is init')

    def f3(self):
        print('f3 in C')


c = C() # A is init B is init C is init
print(C.__bases__) # (<class '__main__.A'>, <class '__main__.B'>)
print(c.name1) # A
print(c.name2) # B
print(c.name3) # C
c.f1() # f1 in A
c.f2() # f2 in B
c.f3() # f3 in C

多继承顺序：从左到右

mro()继承顺序，只有新式类有这个方法

super方法只在python3存在

python3中广度优先继承 D-》B-》C-》A

注意：在python2经典类里（不继承object）深度优先继承，D-》B-》A-》C

python3只有新式类，默认继承object

python2.7经典类（不默认继承object）和新式类共存

class A(object):
    def func(self):
        print('A')


class B(A):
    pass


class C(A):
    def func(self):
        print('C')


class D(B, C):
    pass

print(D.mro()) # [<class '__main__.D'>, <class '__main__.B'>, <class '__main__.C'>, <class '__main__.A'>, <class 'object'>]
d = D()
d.func() # C



==========================================
class A(object):
    def func(self):
        print('A')


class B(A):
    pass


class C(A):
    def func(self):
        print('C')


class D(B, C):
    pass


d = D()
d.func() # C

super的本质：根据调用者的节点位置的广度优先顺序

继承顺序是D-》B-》C-》A

因此super执行顺序就反过来A-》C-》B-》D

class A(object):
    def func(self):
        print('A')


class B(A):
    def func(self):
        super().func()
        print('B')


class C(A):
    def func(self):
        super().func()
        print('C')


class D(B, C):
    def func(self):
        super().func()
        print('D')


d = D()
d.func() # A C B D