# -*- coding: utf-8 -*-
#!/usr/bin/env python

class _Constant(object):
    class _ConstantError(TypeError):
        pass

    def __setattr__(self, name, value):
        if name in self.__dict__:
            raise self._ConstantError, "Can't rebind constant(%s)" % name
        self.__dict__[name] = value

    def __delattr__(self, name):
        if name in self.__dict__:
            raise self._ConstantError, "Can't unbind constant(%s)" % name
        raise NameError, name