How to find dates in the sentence using NLP, RegEx in Python

Question

Hi

Can anyone suggest me some way of finding and parsing dates (in any format, "Aug06", "Aug2006", "August 2 2008", "19th August 2006", "08-06", "01-08-06") in the python.

I came across this question, but it is in perl... http://stackoverflow.com/questions/3445358/extract-inconsistently-formatted-date-from-string-date-parsing-nlp

Any suggestion would be helpful.

Answer 1

from dateutil import parser


texts = ["Aug06", "Aug2006", "August 2 2008", "19th August 2006", "08-06", "01-08-06"]
for text in texts:
    print text, parser.parse(text)


Aug06            2010-08-06 00:00:00
Aug2006          2006-08-28 00:00:00
August 2 2008    2008-08-02 00:00:00
19th August 2006 2006-08-19 00:00:00
08-06            2010-08-06 00:00:00
01-08-06         2006-01-08 00:00:00

And if you want to find these dates in a longer text, then try to search for groups of numbers and months and try to give them to this parser. It will throw an exception if the text does not look like a date.

months = ['January', 'February',...]
months.extend([mon[:3] for mon in months])

# search for numeric dates:
/[\d \-]+/

# search for dates:
for word in sentence.split():
    if word in months:
        ...

Answer 2

This finds all the dates in your example sentence:

for match in re.finditer(
    r"""(?ix)             # case-insensitive, verbose regex
    \b                    # match a word boundary
    (?:                   # match the following three times:
     (?:                  # either
      \d+                 # a number,
      (?:\.|st|nd|rd|th)* # followed by a dot, st, nd, rd, or th (optional)
      |                   # or a month name
      (?:(?:Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)[a-z]*)
     )
     [\s./-]*             # followed by a date separator or whitespace (optional)
    ){3}                  # do this three times
    \b                    # and end at a word boundary.""", 
    subject):
    # match start: match.start()
    # match end (exclusive): match.end()
    # matched text: match.group()

It's definitely not perfect and liable to miss some dates (especially if they are not in English - 21. Mai 2006 would fail, as well as 4ème décembre 1999), and to match nonsense like August Augst Aug, but since nearly everything is optional in your examples, there is not much you can do at the regex level.

The next step would be to feed all the matches into a parser and see if it can parse them into a sensible date.

The regex can't interpret context correctly. Imagine a (stupid) text like You'll find it in box 21. August 3rd will be the shipping date. It will match 21. August 3rd which of course can't be parsed.