(I, Zooko, wrote the lines prepended with "> > ".) Aahz <aahz@pythoncraft.com> wrote:

...

For example, suppose you want to control the ability to listen on sockets for network traffic. If there is a reference (e.g., to an object) that represents the privilege of listening on sockets, then you can give such a reference to one object, allowing that object it to listen on sockets, while withholding it from another object, thus preventing that one from listening on sockets.

Doesn't that only work if the second object never gains a reference to the first object?

This is why real mandatory private data is needed. The second object could have a reference to the first object, and could use the first object through some interface offered by the first object, without being able to access the first object's socket-listener capability. Regards, Zooko http://zooko.com/ ^-- under re-construction: some new stuff, some broken links