2.5

python

#访问限制
bart=Student('Bart Simpson',59)
#修改
bart.score=99
#实例的变量名如果以__开头，就变成了一个私有变量（private），只有内部可以访问
class Student(object):
    def _init_(self,name,score):
        self._name=name
        self.score=score
        def get_name(self):
            return self._name
        def get_score(self):
            return self._score
        def set_score(self,score):
            if 0 <=score <=100:
                self._score=score
            else:
                raise  ValueError('bad score')
        def print_score(self):
            print('%s,%s'%(self._name,self._score))
bart = Student('Bart Simpson', 59)
print('bart.get_name()=',bart.get_name())
bart.set_score(60)
print('bart.getscore()=',bart.get_score())
#继承和多态
class Animal(object):
    def run(self):
        print('Animal is running')
class Dog(Animal):
 def run(self):
  print('Dog is running')
 def eat(self):
     print('Eating meat')
     #可以稍作改动
     class Dog(Animal):
         def run(self):
             print('Dog is running')
      c=Dog()
     isinstance(c,Dog)#True
     print('c is Animal?',isinstance(c,Animal))
     isinstance(c,Animal)#True

     #理解多态
     def run_twice(animal):
         animal.run()
     class   Tortoise(Animal):
         def run(self):
             print('Tortoise is running slowly')


 class Animal(object):
     def run(self):
         print("Animal is running")
     class Dog(Animal):
         pass
         class Cat(Animal):
             def run(self):
                 print('Cat is running')
                 pass
     class Car(object):
     def run(self):
     print('Car is runnng')
     class Stone(object):
         pass
     def run_twice(animal):
         animal.run()
         run_twice(Stone())
         #AttributeError: 'Stone' object has no attribute 'run'

c

  #include<stdio.h>
  int main()
  {
  	int fun(int x,int y,int(*p)(int,int));
  	int max(int,int);
  	int min(int,int);
  	int add(int,int);
  	int a=34,b=-21,n;
  	printf("please choose 1,2 or 3:");
  	scanf("%d",&n);
  	if(n==1) fun(a,b,max);
  	else if(n==2) fun(a,b,min);
  	else if(n==3) fun(a,b,add);
  	return 0;
   } 
   int fun(int x,int y,int(*p)(int,int))//声明形参p是指向函数的指针 
   {    //输入1时调用fun作为实参将两个整数传给fun  还将max作为实参传给形参p 
   	int result;
   	result=(*p)(x,y);
   	printf("%d\n",result);
   }
 int max(int x,int y)
 {
 	int z;
 	if(x>y)z=x;
 	else z=y;
 	printf("max=");
 	return(z);
 }
 int min(int x,int y)
 {
 	int z;
 	if(x<y)
 	z=x;
 	else
 	z=y;
 	printf("max=");
 	return(z);
 }
 int add(int x,int y)
 {
 	int z;
 z=x+y
 printf("sum=");
 return