Regex extracts different parts of a string in sequential order

Question

I have a list of strings

my_strings = [
    "2002-03-04 with Matt",
    "Important: 2016-01-23 with Mary",
    "with Tom on 2015-06-30",
]

I want to extract:

• date (always in yyyy-mm-dd format)
• person (always with person), but I don’t want a “c”

I could do:

import re
pattern = r'.*(\d{4}-\d{2}-\d{2}).*with \b([^\b]+)\b.*'
matched = [re.match(pattern, x).groups() for x in my_strings]

but it fails because the template does not match "with Tom on 2015-06-30".

Questions

How to specify a regular expression pattern to be indifferent to the order in which the date or face is displayed in a string?

and

How to ensure that a method groups()returns them in the same order every time?

I expect the result to look like this:

[('2002-03-04', 'Matt'), ('2016-01-23', 'Mary'), ('2015-06-30', 'Tom')]

Answer 1

regex Python, , 2 .

, , .

(?:.*?(?:(?(1)(?!))\b(\d{4}-\d\d-\d\d)\b|(?(2)(?!))with[ ](\w+))){2}

 (?:
      .*? 
      (?:
           (?(1)(?!))
           \b 
           ( \d{4} - \d\d - \d\d )       # (1)
           \b 
        |  (?(2)(?!))
           with [ ] 
           ( \w+ )                       # (2)
      )
 ){2}

Answer 2

2 ?

my_strings = [
    "2002-03-04 with Matt",
    "Important: 2016-01-23 with Mary",
    "with Tom on 2015-06-30",
]
import re

pattern = r'.*(\d{4}-\d{2}-\d{2})'
dates = [re.match(pattern, x).groups()[0] for x in my_strings]

pattern = r'.*with (\w+).*'
persons = [re.match(pattern, x).groups()[0] for x in my_strings]

output = zip(dates, persons)
print output
## [('2002-03-04', 'Matt'), ('2016-01-23', 'Mary'), ('2015-06-30', 'Tom')]

Answer 3

:

my_strings = [
    "2002-03-04 with Matt",
    "Important: 2016-01-23 with Mary",
    "with Tom on 2015-06-30",
]

import re

alternates = r"(?:\b(\d{4}-\d\d-\d\d)\b|with (\w+)|.)*"

for tc in my_strings:
    print(tc)
    m = re.match(alternates, tc)
    if m:
        print("\t", m.group(1))
        print("\t", m.group(2))

:

$ python test.py
2002-03-04 with Matt
     2002-03-04
     Matt
Important: 2016-01-23 with Mary
     2016-01-23
     Mary
with Tom on 2015-06-30
     2015-06-30
     Tom

, - . , .

Answer 4

For educational purposes only, a non-regular expression approach may include using the dateutilfuzzy parser to extract dates and a nltktoolkit with entity recognition name to extract names. Full code:

import nltk
from nltk import pos_tag, ne_chunk
from nltk.tokenize import SpaceTokenizer
from dateutil.parser import parse


def extract_names(text):
    tokenizer = SpaceTokenizer()
    toks = tokenizer.tokenize(text)
    pos = pos_tag(toks)
    chunked_nes = ne_chunk(pos)

    return [' '.join(map(lambda x: x[0], ne.leaves())) for ne in chunked_nes if isinstance(ne, nltk.tree.Tree)]

my_strings = [
    "2002-03-04 with Matt",
    "Important: 2016-01-23 with Mary",
    "with Tom on 2015-06-30"
]

for s in my_strings:
    print(parse(s, fuzzy=True))
    print(extract_names(s))

Print

2002-03-04 00:00:00
['Matt']
2016-01-23 00:00:00
['Mary']
2015-06-30 00:00:00
['Tom']

This is probably an over complication.