Stop assignment of a class attribute?

[Al Gonzalez]

I can overload the __setattr__ and __delattr__ to make instance attributes
immutable, but I don't see how it can be done for class attributes.  Does
anyone have any ideas?

class Spam:
    """Information that shouldn't be changed"""

    name = "My SPAM!"

    def __init__(self):
        self.X = "test"

    # block setting or deleting of attributes
    def __setattr__(self, name, value):
        if self.__dict__.has_key(name):
            raise TypeError, "Attributes of this class are immutable!\nThey
may not be changed nor deleted."
        else:
            self.__dict__[name]=value

    def __delattr__(self, name):
        if self.__dict__.has_key(name):
            raise TypeError, "Attributes of this class are immutable!\nThey
may not be changed nor deleted."


a = Spam()
a.X = "new test" # will raise an error

Spam.name = "Guindalin" # will not raise an error
a.name = "George!" # will also not raise an error