继承性和多态性

Question

在下面的代码中我试图实现继承和多态属性,我的问题是obj1.hello3("1param","2param") obj1.hello3("11param")这些语句是不正确的,这样做的正确方法是什么

  #!/usr/bin/python

  class test1:
     c,d = ""
     def __init__(self,n):
        self.name = n
        print self.name+"==In a"
     def hello1(self):
        print "Hello1"
     def hello3(self,a,b):
        #print "Hello3 2 param"+str(a)+str(b)
        #print "ab"+str(self.a)+str(self.b)+"Hello1"
        print "Hello3 2 param"

     def hello3(self,a):
        #print "a"+str(self.a)+"Hello1"
        print "Hello3 1 param"+str(a)

  class test2(test1):
     def __init__(self,b):
        test1.__init__(self, "new")
        self.newname = b
        print self.newname+"==In b"
     def hello2(self):
        print "Hello2"

  obj= test1("aaaa")
  obj1=test2("bbbb")
  obj1.hello1()
  obj1.hello2()
  obj1.hello3("1param","2param")
  obj1.hello3("11param")

Answer 1

您正在尝试实现方法重载而不是继承和多态.

Python不支持C++,Java,C#等方式的重载.相反,要在Python中实现所需,您需要使用可选参数.

def hello3(self,a,b=None):
    if b is None:
        print "Hello3 1 param", a
    else:
        print "Hello3 2 param", a, b

...

obj1.hello3("a")#passes None for b param
obj1.hello3("a", "b")