Python经典类和新式类的区别

#从Python的内置类中派生的都是python的新式类
#新式类会广度搜索，也就是一层层的向上搜索

class A(object):
    attr=1
    
class B(A):
    pass

class C(A):
    attr=3

class D(B,C):
    pass

#经典类会深度搜索，遇到一个超类节点向上搜索
class ClassicA:
    attr=1
    
class ClassicB(ClassicA):
    pass

class ClassicC(ClassicA):
    attr=3
    
class ClassicD(ClassicA):
    pass


if __name__ == "__main__":
    d = D()
    print "attr=", d.attr #attr=3
    
    cd = ClassicD()
    print "attr=", cd.attr #attr=1