To be clear. I never said that start-up time wasn't important. Instead, I pointed out that in the previously studied example, the measured impact on start-up time of a single named tuple was a fraction of a millisecond and less than 0.1% of start-up time.

At Guido's behest, I agreed to treat this miniscule component of start-up time as being important and will review and implement some optimizations in the sprints next week. I've agreed to do this even if it comes at the expense of code clarity, complexity, or maintainability. I expect that when I'm done, _source will be a lazily generated attribute and that much of the code currently in the template will be pre-computed. This seems reasonable to me.

FWIW, I've devoted 16 years of my life to optimizing Python and care a great deal about start-up time. I'm not happy about all the Raymond bashing going on in this thread.