I've been teaching programming to someone with zero computer experience. This person had difficulty with mutating variables in Python, so I switched to teaching

I've been teaching programming to someone with zero computer experience. This person had difficulty with mutating variables in Python, so I switched to teaching them Haskell. This person has found the equational reasoning/substitution of Haskell much easier to mentally model. I'd say about two thirds of the people I teach have no difficulties learning Python, and one third do much better learning Haskell because then variables don't vary!