Python Number Conversion Chart

Re:Python Number Conversion Chart by naftaliharris on Saturday April 20, 2013 @02:12PM (#5582278)

And for people who want to convert user entered numbers, like "3.2 million", into strings, I wrote a package especially for that: https://github.com/naftaliharris/numutil

    >>> from numutil import str2num, num2str
    >>> str2num('1.3 million')
    1300000
    >>> str2num('three and a half')
    Fraction(7, 2)
    >>> str2num('123,456.789')
    123456.789
    >>> num2str(1234567, style='newspaper')
    '1.23 million'
    >>> num2str(1234567, style='words')
    'one million, two hundred thirty four thousand, five hundred sixty seven'

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Re:Python Number Conversion Chart by robbles on Saturday April 20, 2013 @05:42PM (#5582919)

Really useful, thanks for making this!

How is the "three and a half" part implemented? Is that just a set of regexes looking for a couple of common patterns? For example, can it parse something like "three and three thirds"?

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Re:Python Number Conversion Chart by naftaliharris on Saturday April 20, 2013 @07:38PM (#5583250)

Sure, I'm glad you like it! :)

str2num parses words by iterating through them once and keeping state about the result so far and what I call the "magnitude". So, for example, when you feed it "three and three thirds", it initializes magnitude and result to zero, chomps the first "three", and then sets magnitude = 3.

If the next word were "million", then it would know that magnitude refers to million, and so it would multiply 3 by 1 million. But the next word is "and", which flushes the magnitude to result, (ie, result += magnitude), and resets the magnitude to zero.

The next word is "three", which, as before, sets magnitude to three. Then the next word is "thirds", so you know that magnitude refers to "thirds", and so you multiply the magnitude by Fraction(1, 3) and add it to result.

  >>> str2num("three and three thirds")
  Fraction(4, 1)

The source for this is here: https://github.com/naftaliharris/numutil/blob/master/numutil...

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