Day27

类的专有方法：

    __init__ 构造函数，在生成对象时调用

    __del__ 析构函数，释放对象时使用

    __repr__ 打印，转换

    __setitem__按照索引赋值

    __getitem__按照索引获取值

    __len__获得长度

    __cmp__比较运算

    __call__函数调用

    __add__加运算

    __sub__减运算

    __mul__乘运算

    __div__除运算

    __mod__求余运算

    __pow__称方

class BaseClass:
    def __init__(self):
        self.name = 'BaseClass'
        print('BaseCalss: Constructor called')
    def getname(self):
        print('BaseCalss: self name equals ' + self.name)

class DerivedClass(BaseClass):
    def __init__(self):
        super().__init__()
        print('DerivedClass: Constructor called')

if __name__ == '__main__':
    class1 = BaseClass()
    class1.getname()

    class2 = DerivedClass()
    class2.getname()

运行结果：

BaseCalss: Constructor called
BaseCalss: self name equals BaseClass
BaseCalss: Constructor called
DerivedClass: Constructor called
BaseCalss: self name equals BaseClass

子类也可以overwrite父类的方法，那么父类的方法就不会被调用，除非手动调用：

class BaseClass:
    def __init__(self):
        self.name = 'BaseClass'
        print('BaseCalss: Constructor called')
    def getname(self):
        print('BaseCalss: self name equals ' + self.name)

class DerivedClass(BaseClass):
    def __init__(self):
        super().__init__()
        print('DerivedClass: Constructor called')
    def getname(self):
        print('self.name init value is ' + self.name)
        self.name = 'DerivedClass'
        print('DerivedClass: self name equals ' + self.name)

if __name__ == '__main__':
    class1 = BaseClass()
    class1.getname()

    class2 = DerivedClass()
    class2.getname()

运行结果：

BaseCalss: Constructor called 
BaseCalss: self name equals BaseClass 
BaseCalss: Constructor called 
DerivedClass: Constructor called 
self.name init value is BaseClass 
DerivedClass: self name equals DerivedClass

python不仅仅支持单继承，还支持多继承

  class BaseClass1:

    def __init__(self):
        self.name1 = 'BaseClass1_Name1'
        self.name = 'BaseClass1_Name'
        print('BaseCalss1: Constructor called')
    def getname1(self):
        print('BaseCalss1: self name1 equals ' + self.name1)
    def getname(self):
        print('BaseCalss1: getname called, name equal ' + self.name)

class BaseClass2:
    def __init__(self):
        self.name2 = 'BaseClass2_Name2'
        self.name = 'BaseClass2_Name'
        print('BaseClass2: Constructor called')
    def getname2(self):
        print('BaseClass2: self name2 equals ' + self.name2)
    def getname(self):
        print('BaseCalss2: getname called, name equal ' + self.name)

class DerivedClass2(BaseClass1, BaseClass2):
    def __init__(self):
        BaseClass1.__init__(self)
        BaseClass2.__init__(self)
        print('DerivedClass: Constructor called')

if __name__ == '__main__':
    class1 = BaseClass1()
    class1.getname1()

    class2 = BaseClass2()
    class2.getname2()

    class3 = DerivedClass2()
    class3.getname1()
    class3.getname2()
    class3.getname()

运行结果：

BaseCalss1: Constructor called 
BaseCalss1: self name1 equals BaseClass1_Name1 
BaseClass2: Constructor called 
BaseClass2: self name2 equals BaseClass2_Name2 
BaseCalss1: Constructor called 
BaseClass2: Constructor called 
DerivedClass: Constructor called 
BaseCalss1: self name1 equals BaseClass1_Name1 
BaseClass2: self name2 equals BaseClass2_Name2 
BaseCalss1: getname called, name equal BaseClass2_Name