Arithmetic Formater

def welcome():
    print("Arithmetic formatter made by DragonBowl for free code camp ")
    selection()


def selection():
    aors = input("Subtraction or Addition A or S :")

    if aors == "A":
        a()
    elif aors == "a":
        a()
    elif aors == "S":
        s()
    elif aors == "s":
        s()
    else:
        print("invalid input")
        input("press enter to continue")
        selection()


def a():
    num1 = int(input("Enter your first number , upto 4 digits :"))
    if num1 > 9999:
        print("number must be smaller than 4 digits")
        a()
    num2 = int(input("Enter your second number ,upto 4 digits :"))
    if num2 > 9999:
        print("number must be smaller than 4 digits")
        a()
    num3 = num1 + num2
    str1 = str(num1)
    str2 = str(num2)
    str3 = str(num3)
    if num1 < 10:
        space1 = ("    ")
        line3 = "-----"
    elif num1 < 100:
        space1 = ("   ")
        line3 = "------"
    elif num1 < 1000:
        space1 = ("  ")
        line3 = "-------"
    elif num1 < 10000:
        space1 = (" ")
        line3 = ("--------")

    if num2 < 10:
        space2 = ("+   ")
    elif num2 < 100:
        space2 = ("+  ")
    elif num2 < 1000:
        space2 = ("+ ")
    elif num2 < 10000:
        space2 = ("+")

    if num3 < 10:
        space4 = ("    ")
    elif num3 < 100:
        space4 = ("   ")
    elif num3 < 1000:
        space4 = ("  ")
    elif num3 < 10000:
        space4 = (" ")

    print(space1, num1)
    print(space2, num2)
    print(line3)
    print(space4, num3)


def s():
    num1 = int(input("Enter your first number , upto 4 digits :"))
    if num1 > 9999:
        print("number must be smaller than 4 digits")
        s()
    num2 = int(input("Enter your second number ,upto 4 digits :"))
    if num2 > 9999:
        print("number must be smaller than 4 digits")
        s()
    if num1 > num2:
        num3 = num1 - num2
    elif num1 < num2:
        num3 = num2 - num1
    elif num1==num2:
        num3=num2-num1
    str1 = str(num1)
    str2 = str(num2)
    str3 = str(num3)
    if num1 < 10:
        space1 = ("    ")
        line3 = "-----"
    elif num1 < 100:
        space1 = ("   ")
        line3 = "------"
    elif num1 < 1000:
        space1 = ("  ")
        line3 = "-------"
    elif num1 < 10000:
        space1 = (" ")
        line3 = ("--------")

    if num2 < 10:
        space2 = ("-   ")
    elif num2 < 100:
        space2 = ("-  ")
    elif num2 < 1000:
        space2 = ("- ")
    elif num2 < 10000:
        space2 = ("-")

    if num3 < 10:
        space4 = ("    ")
    elif num3 < 100:
        space4 = ("   ")
    elif num3 < 1000:
        space4 = ("  ")
    elif num3 < 10000:
        space4=(" ")

    print(space1, num1)
    print(space2, num2)
    print(line3)
    print(space4, num3)


welcome()