making objects unassignable "read-only" (especially when extending)

[Fredrik Lundh]

Johannes Zellner wrote:

> can I make an object read-only, so that
>
>     x = new_value
>
> fails (and x keeps it's orginal value)?

the original x does contain the original value; assignment only changes
the binding in the target namespace.  you cannot override this.

you can control attribute assignment, though:

    x.y = new_value

(via __setattr__ methods/slots on the x object)

</F>