python基础（三）——类的研究

class Employee:         //定义类 以冒号结束
   '所有员工的基类'      //帮助信息
   empCount = 0
   def __init__(self, name, salary):    //调用时初始化，属性有name和salary
      self.name = name
      self.salary = salary
      Employee.empCount += 1

   def displayCount(self):
     print "Total Employee %d" % Employee.empCount      //%格式化打印格式

   def displayEmployee(self):
      print "Name : ", self.name,  ", Salary: ", self.salary

"创建 Employee 类的第一个对象"
emp1 = Employee("Zara", 2000)
"创建 Employee 类的第二个对象"
emp2 = Employee("Manni", 5000)
emp1.displayEmployee()
emp2.displayEmployee()
print "Total Employee %d" % Employee.empCount
emp1.age = 7  # 添加一个 'age' 属性
emp1.age = 8  # 修改 'age' 属性
del emp1.age  # 删除 'age' 属性
hasattr(emp1, 'age')    # 如果存在 'age' 属性返回 True。
getattr(emp1, 'age')    # 返回 'age' 属性的值
setattr(emp1, 'age', 8) # 添加属性 'age' 值为 8
delattr(empl, 'age')    # 删除属性 'age'

//内置类属性
#!/usr/bin/python
# -*- coding: UTF-8 -*-

class Employee:
   '所有员工的基类'
   empCount = 0
    def __init__(self, name, salary):
      self.name = name
      self.salary = salary
      Employee.empCount += 1
   def displayCount(self):
     print "Total Employee %d" % Employee.empCount
   def displayEmployee(self):
      print "Name : ", self.name,  ", Salary: ", self.salary
print "Employee.__doc__:", Employee.__doc__             //帮助文档
print "Employee.__name__:", Employee.__name__           //类名
print "Employee.__module__:", Employee.__module__       //模块
print "Employee.__bases__:", Employee.__bases__         //类的所有父类构成元素
print "Employee.__dict__:", Employee.__dict__           //类的属性

//
#!/usr/bin/python
# -*- coding: UTF-8 -*-

class Parent:        # 定义父类
   parentAttr = 100
   def __init__(self):
      print "调用父类构造函数"
   def parentMethod(self):
      print '调用父类方法'
   def setAttr(self, attr):
      Parent.parentAttr = attr
   def getAttr(self):
      print "父类属性 :", Parent.parentAttr

class Child(Parent): # 定义子类
   def __init__(self):
      print "调用子类构造方法"

   def childMethod(self):
      print '调用子类方法 child method'

c = Child()          # 实例化子类
c.childMethod()      # 调用子类的方法
c.parentMethod()     # 调用父类方法
c.setAttr(200)       # 再次调用父类的方法
c.getAttr()          # 再次调用父类的方法
输出结果
调用子类构造方法
调用子类方法 child method
调用父类方法
父类属性 : 200

//继承多个类
class A:        # 定义类 A
.....
class B:         # 定义类 B
.....
class C(A, B):   # 继承类 A 和 B
.....

//方法重写
#!/usr/bin/python
class parent():
    def mymethod(self):
        print 'this is a test'
    def bp(self):
        print 'how are you'
class child(parent):
    def __init__(self):
        print 'I am bp'
    def mymethod(self):
        print 'this is not a test'
c=child()
c.mymethod()
c.bp()
输出结果
I am bp
this is not a test
how are you

//私有方法和属性
class JustCounter:
    __secretCount = 0  # 私有变量
    publicCount = 0    # 公开变量

    def count(self):
        self.__secretCount += 1
        self.publicCount += 1
        print self.__secretCount

counter = JustCounter()
counter.count()
counter.count()
print counter.publicCount
print counter.__secretCount  # 报错，实例不能访问私有变量
输出结果
1
2
2
Traceback (most recent call last):
  File "test.py", line 17, in <module>
    print counter.__secretCount  # 报错，实例不能访问私有变量
AttributeError: JustCounter instance has no attribute '__secretCount'