I'm using graphql-go/graphql at the moment. Sparse documentation, but everything seems to work correctly. I'm not too familiar with the Python GraphQL stuff, but here I'm writing my own schema and resolvers, so I guess it depends on what you mean from "by scratch."

If you need something off the ground ASAP, maybe look at something like Hasura or Postgraphile: point it at your DB and get the GraphQL resolvers.