python设置常量

# -*- coding:utf-8 -*-
class Const(object):
    class ConsError(TypeError):
        pass

    class ConstCaseError(ConsError):
        pass

    def __setattr__(self, name, value):
        if name in self.__dict__:
            raise (self.ConsError, "Can't change const.%s" % name)
        if not name.isupper():
            raise (self.ConstCaseError, "const name '%s' is not all uppercase" % name)
        self.__dict__[name] = value


const = Const()
const.MY_CONSTANT = 1
const.MY_SECOND_CONSTANT = 2
const.MY_THIRD_CONSTANT = 'a'
const.MY_FORTH_CONSTANT = 'b'