How to regex search strings in different order in python

Question

I have a script that takes in an argument and tries to find a match using regex. On single values, I don't have any issues, but when I pass multiple words, the order matters. What can I do so that the regex returns no matter what the order of the supplied words are? Here is my example script:

import re
from sys import argv

data = 'some things other stuff extra words'

pattern = re.compile(argv[1])
search = re.search(pattern, data)

print search
if search:
    print search.group(0)
    print data

So based on my example, if I pass "some things" as an arg, then it matches, but if i pass "things some", it doesn't matches, and I would like it to. Optionally, I would like it to also return if either "some" or "things" match.

The argument passed could possibly be a regex

You could use itertools.permutations() to generate all possible orderings of the words in data, then call your regexp on each one. — John Gordon
– John Gordon, Commented Dec 28, 2017 at 4:14
why not re.compile("|".join(argv[1:]))? You can pass as many as you want. — Sraw
– Sraw, Commented Dec 28, 2017 at 4:27

Francisco · Accepted Answer · 2017-12-28 04:55:31Z

2

I think you want something like this:

search = filter(None, (re.search(arg, data) for arg in argv[1].split()))

Or

search = re.search('|'.join(argv[1].split()), data)

You can then check the search results, if len(search) == len(argv[1].split()), then it means all patterns matched, and if search is truthy, then it means at least one of them matched.

Ok, I think I got it, you can use a lookahead assertion like this:

>>> re.search('(?=.*thing)(?=.*same)', data)

You can obviously programatically build such regex:

re.search(''.join('(?=.*{})'.format(arg) for arg in argv[1].split()), data)

edited Dec 28, 2017 at 4:55

answered Dec 28, 2017 at 4:33

Francisco

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3 Comments

securisec Over a year ago

This would work if i was not using regex. But argv in this case could be a regex to allow for greater flexibility in the search.

securisec Over a year ago

I like the second option, but it still doesnt answer the question. It will match some or things, but not things some. It is only matching one word then, not both

securisec Over a year ago

perfect! This is exactly what i was looking for!

Sweeper · Accepted Answer · 2017-12-28 04:11:11Z

0

I think it would be better to just create several regexes and match each of them against the string. If any of them matches, you return True.

If you are just trying to match constant strings, the in operator is enough:

'some' in data or 'things' in data

answered Dec 28, 2017 at 4:11

Sweeper

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2 Comments

securisec Over a year ago

I have considered that, but it quickly becomes overwhelming as the argument size grows. As in what is the arg passed is "some things other"? Then it gets too complex.

Sweeper Over a year ago

What becomes too complex? Which solution are you referring to? The in operator or separate regexes? You can use a loop. @securisec

RoadRunner · Accepted Answer · 2017-12-28 05:31:17Z

You could also just split the data text into sublists, and check if the ordering/reverse ordering of search exists in it:

import re

data = 'some, things other stuff extra words blah.'

search = "things, some"

def search_text(data, search):
    data_words = re.compile('\w+').findall(data)
    # ['some', 'things', 'other', 'stuff', 'extra', 'words', 'blah']
    search_words = re.compile('\w+').findall(search)
    # ['things', 'some']

    len_search = len(search_words)

    candidates = [data_words[i:i+len_search] for i in range(0, len(data_words)-1, len_search-1)]
    # [['some', 'things'], ['things', 'other'], ['other', 'stuff'], ['stuff', 'extra'], ['extra', 'words'], ['words', 'blah']]

    return search_words in candidates or search_words[::-1] in candidates

print(search_text(data, search))

Which Outputs:

True

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