Nested handlers without recursion

00_nested_handlers.py

from typing import Any, Callable, Iterable


def noop(next_handler: Callable, *args: Any, **kwargs: Any) -> None:
    pass


def process(handlers: Iterable[Callable], *args: Any, **kwargs: Any) -> None:
    next_args = args
    next_kwargs = kwargs
    continue_processing = True

    def next_handler(*args: Any, **kwargs: Any) -> None:
        nonlocal next_args, next_kwargs, continue_processing
        next_args = args
        next_kwargs = kwargs
        continue_processing = True

    for handler in [*handlers, noop]:
        if not continue_processing:
            break
        continue_processing = False
        handler(next_handler, *next_args, **next_kwargs)  # type: ignore

01_usage.py

def first(next_handler: Callable, client: str, data: str) -> None:
    print("in first")
    print(client, data)
    next_handler(client + "(1)", data + "(1)")


def second(next_handler: Callable, client: str, data: str) -> None:
    print("in second")
    print(client, data)
    next_handler(client + "(2)", data + "(2)")


def third(next_handler: Callable, client: str, data: str) -> None:
    print("in third")
    print(client, data)
    next_handler(client + "(3)", data + "(3)")


process([first, second, third], "client", "data")