如何将整数转换为其语言表示？

def number_to_words(num):
    ones = ["", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"]
    tens = ["", "", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"]
    teens = ["ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"]
    thousands = ["", "thousand", "million", "billion"]

    def helper(num):
        if num < 10:
            return ones[num]
        elif num < 20:
            return teens[num - 10]
        elif num < 100:
            return tens[num // 10] + ('' if num % 10 == 0 else '-' + ones[num % 10])
        else:
            for i, unit in enumerate(thousands):
                if num < 1000 ** (i + 1):
                    break
            return helper(num // (1000 ** i)) + ' ' + unit + (', ' if (num % (1000 ** i)) // 100 == 0 and (num % (1000 ** i)) != 0 else '') + helper(num % (1000 ** i))

    return helper(num)

num = 12345
print(number_to_words(num))