sounds interesting, i'll have a look at the code when i have time. i've mostly done compiler stuff like this with the "one function with a huge switch on the expression type" approach, curious to see what the more OOP-ish way looks like.

btw: wow, that cheatsheet is exactly what i had in mind on my first comment, that's the kind of stuff i'd like in a readme! maybe a few excerpts with a link to the whole thing.

some more remarks if you're interested:

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in that cheatsheet it'd be cool to also show the generated code for each example, maybe in a collapsible box or sth – in that context the actual semantics of a convtools expression are useful to know.

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have you thought about some magic syntactic sugar? the current approach is kind of visually heavy, since you're basically writing an AST by hand. with some __dunder__ hacking you could easily (?) add a "magic" api like

  from convtools.magic import magic as m
  
  c.item('key') ->
  m['key']
  
  c.call_method('foo', ...) ->
  m.meth.foo(...)
  
  c.call_function('bar', ...)  ->
  m.func.bar(...)

or something similar. it might be a bit too magical for some tastes, but if you're constructing a python expression, it kind of makes sense to use python syntax for that