Attached is a partial implementation of PEP 275.

It should offer a slight performance enhancement over
if/elif/else, although it won't be nearly as fast as a
lookup table generated at compile time (as the PEP
suggests). However, it is more flexible than a
compile-time generated lookup table in that it accepts
expressions - not just constants - for each case clause.

No new opcodes were added.

Cheers,
Tom