This is an idea for a method of defining function bodies inside of eg: JSON properties, special files, or other methods. Inspired by a dislike of existing CouchDB query servers for python. Implemented as an ast post-processor.

generated.py

import os
import sys

# Approximate
def _generated_function_name(**__args__):
    spam = __args__['spam']
    eggs = __args__['eggs']
    del __args__
    return os.path.exists(os.path.join(spam, eggs))

source.py

from __args__ import spam, eggs
import os
import sys

return os.path.exists(os.path.join(spam, eggs))