def attrnum(self, attr):
        "Returns the number used for attr, which can be a name, or -n .. n-1."
        if attr < 0:
            return len(self.attrs) + attr
        elif isinstance(attr, str):
            return self.attrnames.index(attr)
        else:
            return attr
def attrnum(self, attr):
        "Returns the number used for attr, which can be a name, or -n .. n-1."
        if attr < 0:
            return len(self.attrs) + attr
        elif isinstance(attr, str):
            return self.attrnames.index(attr)
        else:
            return attr
Returns the number used for attr, which can be a name, or -n .. n-1.