So... this is obviously totally, 100%, like for. real. not. supported. by. Apple. …yet?
But still... I thought it was pretty badass. And, seeing how there's already a Swift buildpack for Heroku you could move some slow code into Swift can call it as a library function. But, you know, not in production or anything. That would be silly, right?
Now, having said that, the actual Python/Swift interop may have bugs. I'll leave that as an exercise to the reader.