menu.py

import os

while True:
    os.system('cls')
    print('0-Exit')
    print('1-Area')
    print('2-Screen Clear')
    ans = input('Choose 0,1,2: ')
    ans = int(ans)

    if ans == 0:
        print('Bye!')
        exit(0)

    if ans == 1:
        r = input('enter r: ')
        r = float(r)
        a = 3.14 * r * r
        print(f'area = {a} for radius = {r}')

    if ans == 2:
        os.system('cls')

    os.system('pause')