python - Ordinal numbers replacement

Question

I am currently looking for the way to replace words like first, second, third,...with appropriate ordinal number representation (1st, 2nd, 3rd). I have been googling for the last week and I didn't find any useful standard tool or any function from NLTK.

So is there any or should I write some regular expressions manually?

Thanks for any advice

Answer 1

Here's a terse solution taken from Gareth on codegolf:

ordinal = lambda n: "%d%s" % (n,"tsnrhtdd"[(n//10%10!=1)*(n%10<4)*n%10::4])

Works on any number:

print([ordinal(n) for n in range(1,32)])

['1st', '2nd', '3rd', '4th', '5th', '6th', '7th', '8th', '9th', '10th',
 '11th', '12th', '13th', '14th', '15th', '16th', '17th', '18th', '19th',
 '20th', '21st', '22nd', '23rd', '24th', '25th', '26th', '27th', '28th',
 '29th', '30th', '31st']