python const

class _const(object):
    class ConstError(TypeError):pass

    def __setattr__(self,name,value):
        if self.__dict__.has_key(name):
             raise self.ConstError,"Can‘t rebind const(%s)" % name
        self.__dict__[name] = value

    def __detattr__(self,name):
        if name in self.__dict__:
             raise self.ConstError,"Can‘t unbind const(%s)" % name
        raise NameError,name

import sys
sys.modules[__name__] = _const()