python面向对象笔记

class Employee:   '所有员工的基类'   **empCount = 0** #类变量，位于类内部方法外部，如Java中static变量，在所有该类实例化对象中公用   def __init__(self, name, salary):#self为该类实例    #self.name、self.salary为类的两个类似Java中public成员变量，可以“实例名.变量名“的形式访问      self.name = name        self.salary = salary      **Employee.empCount** += 1 #公用类变量的使用：类名.变量名   def displayCount(self):     print "Total Employee %d" % Employee.empCount   def displayEmployee(self):  print"Name:",self.name,",Salary:",self.salarypyCharm中.py测试:em=Employee("liu",20) #构造函数中self无需赋值 输出：_init_执行 em.displayCount()  #输出：Total Employee 2em.displayEmployee() #输出：Name: liu ,Salary: 20en=Employee("li",21) #输出：_init_执行en.displayCount()    #输出：Total Employee 3en.displayEmployee() #输出：Name: li ,Salary: 21print em.salary      #输出：20print en.salary      #输出：21print em.empCount    #输出：3print en.empCount    #输出：3修改函数：    def displayEmployee(self):        print "Name:",self.name,",Salary:",self.salary        if(hasattr(self,'age')):#若有属性age则输出            print self.age测试：em.age=12 #直接为实例em添加属性ageen.displayEmployee()#输出：Name: li ,Salary: 21em.displayEmployee()#输出：Name: liu ,Salary: 20 12del em.age #删除实例属性em.displayEmployee() #输出：Name: liu ,Salary: 20再次修改函数：    def displayEmployee(self):        print "Name:",self.name,",Salary:",self.salary        if(hasattr(Employee,'age')):            print Employee.age            Employee.age+=1 测试：em.age=22222print em.displayEmployee()#输出：Name: liu,Salary: 20 Noneprint en.displayEmployee()#输出：Name: li ,Salary: 21None测试另一组：Employee.age=22222print em.displayEmployee()#输出：Name: liu ,Salary: 2022222 #########None？？没搞懂这是什么print en.displayEmployee()#输出：Name: li ,Salary: 2122223  ########None？？没搞懂这是什么