Abusing namedtuple - Yet Another Enum

There's a discussion over at python-ideas about enum. This prompted me to write yet another implementation of enum, this time abusing namedtuple.

try lock

At work, we have several functions that can run only one at a time. We call this "try lock" (or trylock), and had it forever in the Java code.

When we started a Python project, we wanted this functionality. A decorator seems like the right solution. The below try_lock decorator has an optional function that lets you get a finer grained solution on what to lock. It gets the function arguments and returns a key to lock on. If you don't specify keyfn, then there will be just one lock for the function.