What is the reason I am getting a "NameError: name 'int_to_roman' is not defined"? How do I resolve this?

Question

I tried to add a class to this basic Roman Numeral Calculator, but when I try to run the function from the class, I get a NameError. I'm not sure what's going on.

I tried to change the order of the code, but nothing else as I don't know what the reason for the error is.

Also, I don't know why but I can't get the class (below) part into the code block.

class Roman_Number():
    roman_numeral_table = [
    ("M", 1000), ("CM", 900), ("D", 500),
    ("CD", 400), ("C", 100),  ("XC", 90),
    ("L", 50),   ("XL", 40),  ("X", 10),
    ("IX", 9),   ("V", 5),    ("IV", 4),
    ("I", 1)
    ]


    r = input('If you want to go from Roman to Number, enter "1." If you want to go from Number to Roman, enter "2"')

    if r == 1:
        roman_to_int()
    else:
        int_to_roman()

    def int_to_roman():
        number = int(input('Provide Number: '))
        if number < 1 or number > 3999:
            print('Number must be inbetween 1 and 3999')
        else:
            print('Valid Number')

        roman_numerals = []
        for numeral, value in roman_numeral_table:
            while value <= number:
                number -= value
                roman_numerals.append(numeral)

        print(''.join(roman_numerals))

        def roman_to_int():
            pass

I expect it to start running int_to roman(), but I'm just getting an error.

I changed the order and now I'm getting a "roman_numeral_table is not defined." Why and how do I fix this?

Answer 1

You are getting this error, because python executes it blocks in the order of the syntax, you need to define a function before being able call it / cite it. Try this:

def roman_to_int():
      pass

def int_to_roman():
      number = int(input('Provide Number: '))
      if number < 1 or number > 3999:
          print('Number must be inbetween 1 and 3999')
      else:
          print('Valid Number')


class Roman_Number():
    roman_numeral_table = [
    ("M", 1000), ("CM", 900), ("D", 500),
    ("CD", 400), ("C", 100),  ("XC", 90),
    ("L", 50),   ("XL", 40),  ("X", 10),
    ("IX", 9),   ("V", 5),    ("IV", 4),
    ("I", 1)
    ]

    r = input('If you want to go from Roman to Number, enter "1." If you want to go from Number to Roman, enter "2"')

    if r == 1:
        roman_to_int()
    else:
        int_to_roman()

        roman_numerals = []
        for numeral, value in roman_numeral_table:
            while value <= number:
                number -= value
                roman_numerals.append(numeral)

        print(''.join(roman_numerals))