# numberwords.py, V.2.0, Sep 17 2006

import re # for wordsToNumber


def numberToWords(num, spacer=' '):
    "numberToWords(num, spacer=' '): convert a number to its written English name."
    # Just add names to grps list to extend naming capability.
    # Bengt Richter <bokr@accessone.com>
    # http://mail.python.org/pipermail/python-list/2001-August/057835.html

    words = "fnord one two three four five six seven eight nine ten eleven twelve "\
            "thirteen fourteen fifteen sixteen seventeen eighteen nineteen".split()
    # fnord is place holder

    words10 = "fnord fnord twenty thirty forty fifty sixty seventy eighty ninety".split()

    grps = ['', 'thousand', 'million', 'billion', 'trillion']

    maxgrps = len(grps)

    if not num:
        return 'zero'
    if not isinstance(num, (int, long)):
        raise ArithmeticError,"Integer value required."
    if abs(num) >= 1000**maxgrps:
        raise ArithmeticError, "in numberToWords: num is too big."
    if num < 0:
        result = ['minus'] # or 'negative'?
        num = -num
    else:
        result = []

    for grp in xrange(maxgrps):
        grpFactor, num = divmod( num, 1000**(maxgrps-1-grp) )
        if grpFactor:
            hundreds, tens = divmod(grpFactor, 100)
            if hundreds:
                result.extend( [words[hundreds], 'hundred'] )
            if 0 < tens < 20:
                result.append(words[tens])
            elif tens > 0:
                tens, units = divmod(tens, 10)
                if tens and units:
                    result.append( words10[tens] + spacer + words[units] )
                elif tens:
                    result.append( words10[tens] )
                elif units:
                    result.append( words[units] )
            result.append( grps[maxgrps-1-grp] )
        quot = num
    return spacer.join(filter(None, result))


_toNumber_dict = {
    'and':0,
    'zero':0,
    'one':1,
    'two':2,
    'three':3,
    'four':4,
    'five':5,
    'six':6,
    'seven':7,
    'eight':8,
    'nine':9,
    'ten':10,
    'eleven':11,
    'twelve':12,
    'thirteen':13,
    'fourteen':14,
    'fifteen':15,
    'sixteen':16,
    'seventeen':17,
    'eighteen':18,
    'nineteen':19,
    'twenty':20,
    'thirty':30,
    'forty':40,
    'fifty':50,
    'sixty':60,
    'seventy':70,
    'eighty':80,
    'ninety':90,
    'hundred':100,
    'thousand':1000,
}


_spacer = re.compile( "|".join( sorted(_toNumber_dict, key=len, reverse=True) ) )

def wordsToNumber(text):
    """wordsToNumber(text): convert the written English name of a number to the number itself.

    >>> wordsToNumber("One thousand")
    1000
    >>> wordsToNumber("twenty-three")
    23
    >>> wordsToNumber("")
    0
    >>> wordsToNumber("  \\n")
    0
    >>> wordsToNumber("Three thousand, four hundredfiftyseven")
    3457
    >>> wordsToNumber("three thousand, four hundredfiftysette")
    Traceback (most recent call last):
      ...
    ValueError: Invalid element in input string three thousand  four hundredfiftysette
    """
    # Code by Stephen Thorne and Scott David Daniels, improved by leonardo maffi
    # http://groups.google.com/group/comp.lang.python/browse_thread/thread/118161ddcbc92a7c/
    text2 = text.replace("-", " ").replace(",", " ").lower()
    stack = [0]

    def adder(mobj):
        num = _toNumber_dict[mobj.group()]
        if num >= 100:
            stack[-1] *= num
            if num >= 1000:
                stack.append(0)
        else:
            stack[-1] += num
        return ""

    if _spacer.sub(adder, text2).strip():
        raise ValueError, "Invalid element in input string " + text2
    return sum(stack)


if __name__ == '__main__':
    # numberToWords tests
    n = 100
    print "First %d numbers sorted alphabetically:" % n,
    numbers = sorted(xrange(n), key=lambda i: numberToWords(i, spacer=""))
    print " ".join(map(str, numbers)), "\n"

    # wordsToNumber tests
    for i in xrange(10000):
        assert wordsToNumber(numberToWords(i, "")) == i

    for i in xrange(50):
        print i, numberToWords(i, ""), wordsToNumber(numberToWords(i, ""))
    print

    # doctests too
    import doctest
    doctest.testmod()
    print "Tests finished."