Python经典类&新式类继承相关

新式类(广度优先)

image.png

class A(object):
    title = 'A'
    pass


class B(A):
    # title = 'B'
    pass


class C(A):
    # title = 'C'
    pass


class D(A):
    # title = 'D'
    pass


class E(B, C):
    # title = 'E'
    pass


class F(C, D):
    # title = 'F'
    pass


class H(E, F):
    # title = 'H'
    pass


print(H.title)

# H E B F C D A

经典类(深度优先)

image.png

class A:
    # title = 'A'
    pass


class B(A):
    # title = 'B'
    pass


class C(A):
    # title = 'C'
    pass


class D(B, C):
    # title = 'D'
    pass


class E(D):
    # title = 'E'
    pass


class F(D):
    title = 'F'
    pass


class H(E, F):
    pass


print(H.title)
# E D B A C F

image.png

首先找入度为0的点，只有一个A，把A拿出来，把A相关的边剪掉，再找下一个入度为0的点，有两个点（B,C）,取最左原则，拿B，这是排序是AB，然后剪B相关的边，这时候入度为0的点有E和C，取最左。这时候排序为ABE，接着剪E相关的边，这时只有一个点入度为0，那就是C，取C，顺序为ABEC。剪C的边得到两个入度为0的点（DF），取最左D，顺序为ABECD，然后剪D相关的边，那么下一个入度为0的就是F，然后是object。那么最后的排序就为ABECDFobject。

A.__mro__的结果
 
(<class '__main__.A'>, <class '__main__.B'>, <class '__main__.E'>, <class '__main__.C'>, <class '__main__.D'>, <class '__main__.F'>, <type 'object'>)