Adding ${python.branch} without the . to Python groups

[Jeremy Lavergne]

> So ${python.version} is changed if a subport is active?  That's non-intuitive.

If you're defining a port multiple times for various python versions, how else would define it as a variable?

> The ports I'm converting are currently not a subport, does that work regardless?

It should still be accessible, or an equivalent. Just look at the PortGroup files.
http://trac.macports.org/browser/trunk/dports/_resources/port1.0/group