今天在学习设计模式的时候突发奇想，可不可以实现JAVA中的一些内容呢？

比如 final。

final在Java中是一个保留的关键字，可以声明成员变量、方法、类以及本地变量。一旦你将引用声明作final，你将不能改变这个引用了，编译器会检查代码，如果你试图将变量再次初始化的话，编译器会报编译错误。

修饰类

当用final修饰一个类时，表明这个类不能被继承。

class Father(object):    def __new__(cls, *args, **kwargs):        if cls != Father:            raise Exception('This class cannot be inherited.')        return super(Father, cls).__new__(cls, *args, **kwargs)    def __init__(self):        print("Class Father")class Son(Father):    def __init__(self):        print('Class Son')if __name__ == '__main__':    f = Father()    s = Son()

运行结果：

E:\Anaconda\python.exe F:/PythonSpace/ClassMethod/test.pyClass FatherTraceback (most recent call last):  File "F:/PythonSpace/ClassMethod/test.py", line 16, in 
    
         s = Son()  File "F:/PythonSpace/ClassMethod/test.py", line 4, in __new__    raise Exception('This class cannot be inherited.')Exception: This class cannot be inherited.
    

修饰方法

明确禁止该方法在子类中被覆盖。

class Father(object):    def __new__(cls, *args, **kwargs):        if cls != Father and 'show' in cls.__dict__.keys():            raise Exception('This method cannot be rewritten.')        return super(Father, cls).__new__(cls, *args, **kwargs)    def show(self):        print("Class Father")class Son(Father):    def show(self):  #删除后就不会报错        passif __name__ == '__main__':    f = Father()    f.show()    s = Son()    s.show()

运行结果：

E:\Anaconda\python.exe F:/PythonSpace/ClassMethod/test.pyTraceback (most recent call last):Class Father  File "F:/PythonSpace/ClassMethod/test.py", line 17, in 
    
         s = Son()  File "F:/PythonSpace/ClassMethod/test.py", line 4, in __new__    raise Exception('This method cannot be rewritten.')Exception: This method cannot be rewritten.
    

修饰变量

对于一个final变量，其数值一旦在初始化之后便不能更改。

class Father(object):    __final = 1    def __setattr__(self, key, value):        if key == '_Father__final':            raise Exception('Property cannot be changed after initialization.')        else:            self.__dict__[key] = value    def __init__(self):        self.__final = 2if __name__ == '__main__':    f = Father()

运行结果：

E:\Anaconda\python.exe F:/PythonSpace/ClassMethod/test.pyTraceback (most recent call last):  File "F:/PythonSpace/ClassMethod/test.py", line 14, in 
    
         f = Father()  File "F:/PythonSpace/ClassMethod/test.py", line 10, in __init__    self.__final = 2  File "F:/PythonSpace/ClassMethod/test.py", line 5, in __setattr__    raise Exception('Property cannot be changed after initialization.')Exception: Property cannot be changed after initialization.
    

结束语

以上只是本人观点，难免有不足之处，只做参考，不做考究。