Why is the response type passed to the method as a variable?

Question

Python

Most web frameworks use the following construct: It's not clear why resp is always passed into the handler function. It's the same answer. We do not accept it, but must return it.
def on_get(self, req, resp):

Answer 1

So that you do not copy-paste the response constructor everywhere, a blank is passed. And yes, not "in the majority", but in asynchronous / non-blocking ones, because in synchronous response classes are primitive and are used only after the response is completed.

Answer 2

This is the object that you must complete. In functional languages, this could well be a return value, but it is difficult to pass it to another asynchronous function. Synthetic example:
From the less synthetic examples, the need to make an asynchronous request in order to eventually form a response