Recipe 252158 revision 1

# requires Python 2.2+

def frozen(set):
    "Raise an error when trying to set an undeclared name."
    def set_attr(self,name,value):
        if hasattr(self,name):
            set(self,name,value) 
        else:
            raise AttributeError("You cannot add attributes to %s" % self)
    return set_attr

class Frozen(object):
    """Subclasses of Frozen are frozen, i.e. it is impossibile to add
     new attributes to them and their instances."""
    __setattr__=frozen(object.__setattr__)
    class __metaclass__(type):
        __setattr__=frozen(type.__setattr__)

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History

• revision 1 (20 years ago)