milestone_steps.py

import math
import random

MILESTONE_DEFAULT_PROGRESSION = [1, 2, 5]


def milestone_nearest(x, before=True, progress=None):
    progress = progress or MILESTONE_DEFAULT_PROGRESSION
    x = int(x)
    if x <= 0:
        return MILESTONE_DEFAULT_PROGRESSION[0]

    mag = 10 ** int(math.log10(x))
    if before:
        delta = -1
        mag *= 10
    else:
        delta = 1
    i = 0

    while True:
        step = progress[i]
        y = step * mag
        if before and x >= y:
            return y
        if not before and x < y:
            return y
        i += delta
        if i < 0:
            i = len(progress) - 1
            mag //= 10
        elif i >= len(progress):
            i = 0
            mag *= 10


def main():
    before = False
    pr = [1, 2, 5]
    while True:
        r = input('next?').strip()
        if not r:
            x = int(random.uniform(0, 1000))
        else:
            try:
                x = int(r)
            except ValueError:
                print('enter number!')
                continue

        print(f'{x:<10} => {milestone_nearest(x, before, pr)}')
        print('-' * 100)


if __name__ == '__main__':
    main()