...system().

An interface for this function already exists in the standard module os --- it was chosen as a simple and straightfoward example.

...borrow

The metaphor of ``borrowing'' a reference is not completely correct: the owner still has a copy of the reference.

...completely.

Checking that the reference count is at least 1 does not work --- the reference count itself could be in freed memory and may thus be reused for another object!

...tuple.

These guarantees don't hold when you use the ``old'' style calling convention --- this is still found in much existing code.

...directory.

Check the manual page of the dl package for details.

guido@cwi.nl