DCP10 - Calling function after n milliseconds

# Implement a job scheduler, which takes in a function f and an integer n
# and calls f after n milliseconds

from timeit import default_timer as timer
def f(n):
    if n < 0 or n != int(n):
        return "Error using the function 'f'"
    elif n == 0:
        return "Ending time: " + str(timer())
    else:
        start = timer()
        print("Starting time = " + str(start))
        while 1000 * (timer() - start) < n:
            continue
        return f(0)

# MAIN FUNCTION
millis = [10, 50, 500, 1000, 3000, 5000]
for milli in millis:
    print("**** milliseconds = " + str(milli) + " ****")
    print(f(milli))
    print()