Number To Word

Challenge: Medium
Concepts: General
Download: numword.zip
Solution: Number To Word: Solution

Write a function to convert an integer number to the word representation.

We should handle zero:

>>> num_word(0)
'zero'

And numbers under a thousand:

>>> num_word(2)
'two'

>>> num_word(-2)
'negative two'

>>> num_word(11)
'eleven'

>>> num_word(20)
'twenty'

>>> num_word(100)
'one hundred'

>>> num_word(121)
'one hundred twenty one'

And numbers over a thousand:

>>> num_word(1256)
'one thousand two hundred fifty six'

>>> num_word(100001)
'one hundred thousand one'

>>> num_word(1000000)
'one million'

And all numbers ranging from -999,999,999,999 to 999,999,999,999 (you can stop there):

>>> num_word(-1234567890)  
'negative one billion two hundred thirty four million
five hundred sixty seven thousand eight hundred ninety'

>>> num_word(999999999999)  
'nine hundred ninety nine billion nine hundred ninety nine million
nine hundred ninety nine thousand nine hundred ninety nine'

We’ve provided a file, numword.py, with a function, num_word:

def num_word(num):
    """Convert word to number."""

This is just a stub, though—implement it.