Retriable class decorator, which would allow declaration time AND runtime resetting of decorator properties.

retriable.py

import time
from functools import wraps, update_wrapper


def scaled_retries(attempts, sleeptime, sleepscale):
    scaled_sleeptime = sleeptime
    for attempt_no in range(attempts):
        yield attempt_no + 1, scaled_sleeptime
        scaled_sleeptime *= sleepscale

        # don't need to sleep if this was the last attempt
        if attempt_no < attempts - 1:
            time.sleep(scaled_sleeptime)


class Retriable:
    def __init__(
            self,
            func,
            attempts=5,
            sleeptime=1,
            sleepscale=1.5,
            cleanup=None,
            fail_fast_exceptions=None
    ):
        self.func = func
        self.attempts = attempts
        self.sleeptime = sleeptime
        self.sleepscale = sleepscale
        self.cleanup = cleanup
        self.fail_fast_exceptions = fail_fast_exceptions
        update_wrapper(self, func)

    def __call__(self, *args, **kwargs):
        retries = scaled_retries(self.attempts, self.sleeptime, self.sleepscale)
        for attempt_no, scaled_sleeptime in retries:
            # noinspection PyBroadException
            try:
                return self.func(*args, **kwargs)
            except Exception as e:
                if self.fail_fast_exceptions and isinstance(e, self.fail_fast_exceptions):
                    raise
                if self.cleanup:
                    self.cleanup(attempt_no, scaled_sleeptime, e)
                if attempt_no == self.attempts:
                    raise
                    
if __name__ == '__main__':
    count = 0

    @Retriable
    def sketchy_sum(a, b):
        global count
        if count < 4:
            count += 1
            raise FileNotFoundError()
        return a + b

    def log(_name, _args, _kwargs, attempt_no, next_sleep, e):
        print(f'sketchy sum attempt {attempt_no} failed with {e} and will retry after {next_sleep}')
    
    sketchy_sum.cleanup = log
    # safe_sum = retriable(cleanup=log, fail_fast_exceptions=(FileNotFoundError,))(sketchy_sum)
    # safe_sum = retriable(cleanup=log)(sketchy_sum)
    print(sketchy_sum(2, 2))