integer to english words

🏠

return a list with 0 or 1 items
slicing to prevent list index out of range

Stefan Pochmann's solution:

 1 def numberToWords(self, num):
 2     to19 = 'One Two Three Four Five Six Seven Eight Nine Ten Eleven Twelve ' \
 3            'Thirteen Fourteen Fifteen Sixteen Seventeen Eighteen Nineteen'.split()
 4     tens = 'Twenty Thirty Forty Fifty Sixty Seventy Eighty Ninety'.split()
 5     def words(n):
 6         if n < 20:
 7             return to19[n-1:n]
 8         if n < 100:
 9             return [tens[n/10-2]] + words(n%10)
10         if n < 1000:
11             return [to19[n/100-1]] + ['Hundred'] + words(n%100)
12         for p, w in enumerate(('Thousand', 'Million', 'Billion'), 1):
13             if n < 1000**(p+1):
14                 return words(n/1000**p) + [w] + words(n%1000**p)
15     return ' '.join(words(num)) or 'Zero'