Extracting date from a string in Python

How can I extract the date from a string like "monkey 2010-07-10 love banana"? Thanks!

Using python-dateutil:

In [1]: import dateutil.parser as dparser

In [18]: dparser.parse("monkey 2010-07-10 love banana",fuzzy=True)
Out[18]: datetime.datetime(2010, 7, 10, 0, 0)

Invalid dates raise a ValueError:

In [19]: dparser.parse("monkey 2010-07-32 love banana",fuzzy=True)
# ValueError: day is out of range for month

It can recognize dates in many formats:

In [20]: dparser.parse("monkey 20/01/1980 love banana",fuzzy=True)
Out[20]: datetime.datetime(1980, 1, 20, 0, 0)

Note that it makes a guess if the date is ambiguous:

In [23]: dparser.parse("monkey 10/01/1980 love banana",fuzzy=True)
Out[23]: datetime.datetime(1980, 10, 1, 0, 0)

But the way it parses ambiguous dates is customizable:

In [21]: dparser.parse("monkey 10/01/1980 love banana",fuzzy=True, dayfirst=True)
Out[21]: datetime.datetime(1980, 1, 10, 0, 0)

If the date is given in a fixed form, you can simply use a regular expression to extract the date and "datetime.datetime.strptime" to parse the date:

import re
from datetime import datetime

match = re.search(r'\d{4}-\d{2}-\d{2}', text)
date = datetime.strptime(match.group(), '%Y-%m-%d').date()

Otherwise, if the date is given in an arbitrary form, you can't extract it easily.

For extracting the date from a string in Python; the best module available is the datefinder module.

You can use it in your Python project by following the easy steps given below.

Step 1: Install datefinder Package

pip install datefinder

Step 2: Use It In Your Project

import datefinder

input_string = "monkey 2010-07-10 love banana"
# a generator will be returned by the datefinder module. I'm typecasting it to a list. Please read the note of caution provided at the bottom.
matches = list(datefinder.find_dates(input_string))

if len(matches) > 0:
    # date returned will be a datetime.datetime object. here we are only using the first match.
    date = matches[0]
    print date
else:
    print 'No dates found'

note: if you are expecting a large number of matches; then typecasting to list won't be a recommended way as it will be having a big performance overhead.

Using Pygrok, you can define abstracted extensions to the Regular Expression syntax.

The custom patterns can be included in your regex in the format %{PATTERN_NAME}.

You can also create a label for that pattern, by separating with a colon: %s{PATTERN_NAME:matched_string}. If the pattern matches, the value will be returned as part of the resulting dictionary (e.g. result.get('matched_string'))

For example:

from pygrok import Grok

input_string = 'monkey 2010-07-10 love banana'
date_pattern = '%{YEAR:year}-%{MONTHNUM:month}-%{MONTHDAY:day}'

grok = Grok(date_pattern)
print(grok.match(input_string))

The resulting value will be a dictionary:

{'month': '07', 'day': '10', 'year': '2010'}

If the date_pattern does not exist in the input_string, the return value will be None. By contrast, if your pattern does not have any labels, it will return an empty dictionary {}

References:

• pygrok (Github)
• pygrok Preinstalled Definitions (Github)