I can's seem to get this simple calculator to work. Can anyone assist? Thank you!

# My Calculator Script: version 1.0




def first():
    global first_num
    first_num = (input("Please enter the first number:\n"))
    int(first_num)
    if first_num == 0:
        print("Error, please choose a value higher than 0.\n")
        first()

def operators():

    global enter_op
    enter_op = input("Please enter an operator. You can choose: -, +, /, or *.\n")
    str(enter_op)
    if enter_op not in ("-", "+", "/", "*"):
        print("Error, please enter a valid operator. You can choose from -, +, /, or *\n")
        operators()

def second():

    global second_num
    second_num = input("Please enter the second number:\n")
    int(second_num)
    if second_num == 0:
        print("Error, please choose a value higher than 0.\n")
        second()

def solution():


    if enter_op == ("+"):
        print(first_num + second_num)
    elif enter_op == ("-"):
        print(first_num - second_num)
    elif enter_op == ("/"):
        print(first_num / second_num)
    elif enter_op == ("*"):
        print(first_num * second_num)
    else:
        print("What happened!")


first()
operators()
second()
solution()