timer.py

class Timer:
    def __enter__(self):
        self.__interval = None
        self.__start = time.perf_counter()
        return self

    def __exit__(self, *args):
        self.__end = time.perf_counter()
        self.__interval = self.__end - self.__start
        print(self.__interval, file=sys.stderr)
    
    def __call__(self):
        return self.__interval
    
    def __str__(self):
        return str(self.__interval)