constant.py

# coding:utf-8

class _Const(object):

    class ConstantError(TypeError): pass

    def __setattr__(self, name, value):
        if self.__dict__.has_key(name):
            raise self.ConstantErrorr("can't change const value '%s'." % name)
        if not name.isupper():
            raise self.ConstantError("constant name '%s' is not all uppercase." % name)
        object.__setattr__(self, name, value)


const = _Const()