collections.ChainMap from #python is pretty cool. One place I use it when I want to merge configuration from CLI, environment vars, and config files. You can do that like this...
@dmwyatt it's pretty much *the* use case for ChainMap, I always thought!

@isagalaev

That might be! The first time I ever used extensively was when I was writing a template engine. (Think Jinja2 or Django)

@dmwyatt ah, stacked contexts, that too.
@dmwyatt Nice ! Didn’t now about this , thank you 🙏