num2words.py

#!/usr/bin/python

zeroTo19 = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine",
"ten", "eleven", "twelve", "thirteen", "fourteeen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"]
tens = [ "", "", "twenty", "thirty", "fourty", "fifty", "sixty", "seventy", "eighty", "ninety" ]
denoms = [ (1000000000000, "trillion"), (1000000000, "billion"), (1000000, "million"), (1000, "thousand"), (100, "hundred") ]

def num2words(n):
    if n<20:
        return zeroTo19[n]

    words = None

    if n<100:
        t, n1 = divmod(n, 10)
        words = tens[t]
        if n1>0: words += " " + zeroTo19[n1]
        return words

    for (d, w) in denoms:
        if n >= d:
            den, rem = divmod(n, d)
            words = num2words(den) + " " + w
            if rem >0: words += " " + num2words(rem)
            return words

if __name__ == '__main__':
    import random
    import timeit

    import platform
    from multiprocessing import cpu_count

    rand = random.Random()
    rand.seed()

    test_data=[
(1000000000001, "one trillion one"),
(1000000000000, "one trillion"),
(999999999999, "nine hundred ninety nine billion nine hundred ninety nine million nine hundred ninety nine thousand nine hundred ninety nine"),
(1000000001, "one billion one"),
(1000000000, "one billion"),
(999999999, "nine hundred ninety nine million nine hundred ninety nine thousand nine hundred ninety nine"),
(1000001, "one million one"),
(1000000, "one million"),
(999999, "nine hundred ninety nine thousand nine hundred ninety nine"),
(1001, "one thousand one"),
(1000, "one thousand"),
(999, "nine hundred ninety nine"),
(101, "one hundred one"),
(100, "one hundred"),
(99, "ninety nine"),
(405478, "four hundred five thousand four hundred seventy eight")
    ]

    for (n, words) in test_data:
        assert(num2words(n) == words)
        print n, num2words(n)

    r = rand.randint(0, 1000000000000)
    print r, ":", num2words(r)

    def benchmark():
        r = rand.randint(0, 1000000000000)
        num2words(r)

    print "========================================================="
    print "Benchmarking on", cpu_count(), "CPU(s)", platform.uname()
    t = timeit.Timer(benchmark)
    print(t.timeit())