python3以不存在经典类
class A:
pass
class B(A):
pass
class C(A):
pass
class D(B, C):
pass
class E:
pass
class F(D, E):
pass
class G(F, D):
pass
class H:
pass
class Foo(H, G):
pass
分析
类的MRO顺序是 foo->H->G->F->D->B->A->C->E,从左往右的顺序
python中的新式类的MRO是采用的C3算法来完成的
class A:
pass
class B(A):
pass
class C(A):
pass
class D(B, C):
pass
class E(C,A):
pass
class F(D, E):
pass
class G(E):
pass
class H(G,F):
pass
print(H.__mro__)
3C算法
L(H) = H + L(G) + L(F) + GF L(G) = G + L(E) + E L(F) = F + L(D) + L(E) + DE L(D) = D + L(B) + L(C) + BC L(B) = B + L(A) + A L(A) = A L(E) = E + L(C) + L(A) + CA L(C) = C + L(A) + A
加法:merge(), 拿第一项的第一位和后面每项的除了第一位比较. 如果没有出现, 则该位元素算出
如果出现了. 此时开始下一项的第一位继续和后面每一项的除了第一位比较:
用头和后面身体比较
转换
L(C) = C + A + A #CA L(E) = E + CA + A #ECA L(A) = A #A L(B) = B + A + A #BA L(D) = D + BA + CA + BC #DBCA L(F) = F + DBCA + ECA + DE #FDBECA L(G) = G + ECA + E #GECA L(H) = H + GECA + FDBECA + GF #HGFDBECA
最终结果
H->G->F->D->B->E->C->A
打印结果
(<class ‘__main__.H‘>, <class ‘__main__.G‘>, <class ‘__main__.F‘>, <class ‘__main__.D‘>, <class ‘__main__.B‘>, <class ‘__main__.E‘>, <class ‘__main__.C‘>, <class ‘__main__.A‘>, <class ‘object‘>)
super()可以帮我们执行MRO中下一个父类的方法.
class Base1:
def chi(self):
print("我是Base1")
class Base2:
def chi(self):
print("我是Base2")
class Base3:
def chi(self):
print("我是Base3")
class Bar(Base1,Base2,Base3):
def chi(self):
print("我是Bar1")
super(Bar,self).chi()
print("我是Bar2")
b = Bar()
b.chi()
print(Bar.__mro__)
打印
我是Bar1 我是Base1 我是Bar2 (<class ‘__main__.Bar‘>, <class ‘__main__.Base1‘>, <class ‘__main__.Base2‘>, <class ‘__main__.Base3‘>, <class ‘object‘>)
class Init(object):
def __init__(self, v):
print("init")
self.val = v
class Add2(Init):
def __init__(self, val):
print("Add2")
super(Add2, self).__init__(val)
print(self.val)
self.val += 2
class Mult(Init):
def __init__(self, val):
print("Mult")
super(Mult, self).__init__(val) # Haha
self.val *= 5
class HaHa(Init):
def __init__(self, val):
print("哈哈")
super(HaHa, self).__init__(val) # Init
self.val /= 5
class Pro(Add2,Mult,HaHa):
pass
class Incr(Pro):
def __init__(self, val):
super(Incr, self).__init__(val)
self.val += 1
a = Incr(5)
print(a.val)
b = Add2(2)
print(b.val)
打印
Add2 Mult 哈哈 init 5.0 8.0 Add2 init 2 4
结论
不管super()写在哪儿. 在哪儿执行. 一定先找到MRO列表. 根据MRO列表的顺序往下找. 否则一切都是错的
原文：https://www.cnblogs.com/xiaoqianbook/p/10169175.html