word to digit module

Stephen Thorne stephen.thorne at gmail.com
Wed Dec 22 06:50:58 CET 2004

On Wed, 22 Dec 2004 10:27:16 +0530, Gurpreet Sachdeva
<gurpreet.sachdeva at gmail.com> wrote:
> Is there any module available that converts word like 'one', 'two',
> 'three' to corresponding digits 1, 2, 3??

This seemed like an interesting problem! So I decided to solve it.

I started with 
http://www.python.org/pycon/dc2004/papers/42/ex1-C/ which allowed me
to create a nice test suite.
import num2eng
for i in range(40000):
    e = num2eng.num2eng(i)
    if toNumber(e) != i:
        print e, i, toNumber(e)

once this all important test suite was created I was able to knock up
the following script. This is tested up to 'ninty nine thousand nine
hundred and ninty nine'. It won't do 'one hundred thousand', and isn't
exceptionally agile. If I were to go any higher than 'one hundred
thousand' I would probably pull out http://dparser.sf.net/ and write a

translation = {

def toNumber(s):
    items = s.replace(',', '').split()
    numbers = [translation.get(item.strip(), -1) for item in items if
    if -1 in numbers:
        raise ValueError("Invalid string '%s'" % (s,))

    if 1000 in numbers:
        idx = numbers.index(1000)
        hundreds = numbers[:idx]
        numbers = numbers[idx+1:] + [1000*x for x in hundreds]

    if 100 in numbers:
        idx = numbers.index(100)
        hundreds = numbers[:idx]
        numbers = numbers[idx+1:] + [100*x for x in hundreds]

    return sum(numbers)

Stephen Thorne

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