How do I get the return value when using Python exec on the code object of a function?

Question

For testing purposes I want to directly execute a function defined inside of another function.

I can get to the code object of the child function, through the code (

Answer 1

Something like this can work:

def outer():
    def inner(i):
        return i + 10


for f in outer.func_code.co_consts:
    if getattr(f, 'co_name', None) == 'inner':

        inner = type(outer)(f, globals())

        # can also use `types` module for readability:
        # inner = types.FunctionType(f, globals())

        print inner(42) # 52

The idea is to extract the code object from the inner function and create a new function based on it.

Additional work is required when an inner function can contain free variables. You'll have to extract them as well and pass to the function constructor in the last argument (closure).