I considered Hasura but went with postgraphile (https://github.com/graphile/postgraphile) because it's written in JavaScript with a plugin architecture, meaning I can easily add my own plugins into the system down the road. Creating a JavaScript plugin sounds much less daunting that looking into a mature Haskell codebase.
Hey, have you seen the preview docs of hasura actions? It has a small example of integrating python (or for that matter, any language) for custom mutations.
