Regular expression for extracting no. of days, months and years left

I'm trying to write a regular expression that extracts the number of time left for something, which can be days, months or years.

For eg, there is a sentence- "This product has a shell life of 21 days or 21 (twenty-one) days or twenty-one days or 21 months, 21 years or five days or 5 (five) days or five (5) days or five(5) days."

I know this is a funny sentence but the point is I want to extract the durations which is in the above sentence.

I have written a regular expression (?:\w*\-?\w*\s*\(\s*\d+\s*\w*\)\s*\w*|\b\d*\s+\w*\d*)\s*(?:year|month|day)s? but its not extracting 5 (five) days or the duration which have a digit followed by (words). Can anyone help with the regex ?

Thanks in advance

Solution

If you want to match the parts in the example data, you might use

\w+(?:-\w+)?\s*(?:\(\w+(?:-\w+)?\)\s+)?(?:year|month|days)s?\b

The pattern matches:

\w+(?:-\w+)? Match 1+ word char with an optional - and word chars
\s* Match optional whitespace chars
(?:\(\w+(?:-\w+)?\)\s+)? Optionally match from ( till ) where there can be word chars with an optional - and word chars in between
(?:year|month|days)s? Match any of the alternatives and an optional s
\b A word boundary to prevent a partial match

See a regex demo or a Python demo

Example

import re
from pprint import pprint

regex = r"\w+(?:-\w+)?\s*(?:\(\w+(?:-\w+)?\)\s+)?(?:year|month|days)s?\b"

s = "This product has a shell life of 21 days or 21 (twenty-one) days or twenty-one days or 21 months, 21 years or five days or 5 (five) days or five (5) days or five(5) days."

pprint (re.findall(regex, s))

Output

['21 days',
 '21 (twenty-one) days',
 'twenty-one days',
 '21 months',
 '21 years',
 'five days',
 '5 (five) days',
 'five (5) days',
 'five(5) days']

Note that \s could possible also match a newline, and \w can match digits and chars a-z so there can be a broad range of matches.