Comment by mcanouil

With a constructor, you get to document/validate. A plain dictionary makes this harder or virtually impossible (you most often will silently fail).

https://m.canouil.dev/gribouille/reference/core/aes.html

I already drifted apart from ggplot2/plotnine in many ways, I don't mind as long as it's not confusing.

I've opened a GitHub issue about this question (no ansers at this point): https://github.com/mcanouil/gribouille/issues/143