flag True while flag choice input If you would like to convert to pres

flag = True
while flag:
    choice = (input('If you would like to convert F to C, press C. If it is C to F, press F. '))
    if choice.isdigit():
        print('Invalid input!')
    elif choice == ' ':
       print('Invalid input')
    else:
        print('Print the number you wish to convert to ' + choice + '.')
        flag = False


def farengeitToCelcium(farengeit):
    celcium = (farengeit - 32) / 1.8
    return round(celcium, 1)


def celciumToFarengeit(celcium):
    farengeit = celcium * 1.8 + 32
    return round(farengeit, 1)


if choice == 'F':
    celcium = float(input())
    print(celciumToFarengeit(celcium))
elif choice == 'C':
    farengeit = float(input())
    print(farengeitToCelcium(farengeit))
else:
    print('Invalid input! Please choose F or C. ')