To do this in Python, couldn't you just fork the Python process after initializing the web framework etc. and handle the request in the forked process? Optionally keep a pool of pre-forked worker processes so that the request doesn't have to wait for the forking. Sort of like Android's zygote process.
In principle, yes. But forking an application server gets tricky -- some resources (like database connections) aren't fork-safe, and need to be recreated after forking.
Fork is kind of expensive in most OS, even it's relative cheap compared to start a new process from scratch, but still much slower than few function calls.
