python内部类

• 在类的内部定义的类

内部类的实例化方法

1. 直接使用外部类调用内部类
   object_name = outclass_name.inclass_name()
2. 先对外部类进行实例化，在实例化内部类
   out_name = outclass_name()
in_name = out_name.inclass_name()
in_name.method()

类的内置方法

1. __str__() : 给类设置返回值

#!/usr/bin/python
#coding:utf8

class MyClass(object):
    name = 'Karl'
    id = 007
    __age = 18

    def think(self):
        self.__age = 28
        name = 'John'
        print "My name is %s" %self.name
        print "My age is %s" %self.__age

    def __secret(self):
        print "I can tell you a secret!"

    def tell(self):
        self.__secret()

    def __str__(self):
        return "This is MyClass"        # 只能用return，不能用print


    @staticmethod
    def test():                 # 注意没带参数self
        print "This is a static func"

    @classmethod
    def test2(self):
        print "This is a class func"

#    cm = classmethod(test2)    # 类方法

#    sm = staticmethod(test)    # 静态方法

me = MyClass()
print me

[root@KARL ~]# python u3.py
This is MyClass

# 若没有__str__()方法，则打印如下
[root@KARL ~]# python u3.py
<__main__.MyClass object at 0x7f25c440fcd0>

2. __init__() : 构造函数(可选)，用于初始化类的内部状态
3. __del__() : 析构函数(可选)，用于释放对象占用的资源

  1 #!/usr/bin/python
  2 #coding:utf8
  3
  4 class MyClass(object):
  5     name = 'Karl'
  6     id = 007
  7     __age = 18
  8
  9
 10     def tell(self):
 11         self.__secret()
 12
 13     def __str__(self):
 14         return "This is MyClass"        # 只能用return，不能用print
 15
 16     def __init__(self):
 17         self.name = "Default"
 18         print "Init ..."
 19         print "The name is %s" %self.name
 20
 21     def __del__(self):
 22         print "Del ..."
 23
 24
 25     @staticmethod
 26     def test():                 # 注意没带参数self
 27         print "This is a static func"
 28
 29     @classmethod
 30     def test2(self):
 31         print "This is a class func"
 32
 33 me = MyClass()    # 仅仅实例化类

[root@KARL ~]# python u3.py
Init ...
The name is Default
Del ...

类的继承

• 子类继承类父类的所有公有属性和方法
• 继承实现类代码复用
• class MyClass(ParentClass1 [, ParentClass2, ...])
• 若父类定义了__init__()方法，子类必须显示调用父类的__init__()方法
• 若子类需要扩展父类的行为，可添加__init__()方法的参数
• 子类调用父类的构造函数有以下2种方式

1. ParentClass.__init__(self [, args ...])
2. super(MyClass, self).__init__([args ...])

#!/usr/bin/python
#coding:utf8

class MyClass(object):
    name = 'Karl'
    id = 007
    __age = 18


    def __str__(self):
        return "This is MyClass"        # 只能用return，不能用print

    def __init__(self, c):
        self.name = "Default"
        print "Init ..."
        print "The name is %s" %self.name
        print "I am %s" %c

    def __del__(self):
        print "Del ..."


    @staticmethod
    def test():                 # 注意没带参数self
        print "This is a static func"

    @classmethod
    def test2(self):
        print "This is a class func"

class SonClass(MyClass):
    def __init__(self):
        # MyClass.__init__(self, 'black')
        super(SonClass, self).__init__('black')   # 父类名后必须带有(object)时，才能使用super，注意super的参数用子类名

me = SonClass()   # 仅仅实例化类

[root@KARL ~]# vim u3.py
[root@KARL ~]# python u3.py
Init ...
The name is Default
I am black
Del ...

多重继承

• 多重继承时，若多个父类定义了__init__()方法时，子类只执行第一个类的__init__()方法