Check if any element of an array exists in a string (Python)

Question

NOTE: I found some similar questions, but nothing specifically for Python nor this specific scenario.

Here is a small example (working) snippet that searches for strings (from an array of strings) within a larger string.

#!/usr/bin/python

matches = [
    "NEEDLE1",
    "NEEDLE2",
    "N33DL3"
]

haystack = 'this is a haystack, there may or may not be a noodley needle around here. Needless to say I hate N33DL3 people'

for match in matches:
    if match in haystack:
        print("Found")

Question: Is there a "better" way to do this without having to loop through (for match in matches) each array element?

Edit: The accepted answer works and is fast. Here are the timings:

# Ran the following: 

starttime = timeit.default_timer()
for match in matches:
    if match in haystack:
        print("Found with looping in ", timeit.default_timer() - starttime)

starttime = timeit.default_timer()
if any(match in haystack for match in matches):
    print("Found with any() in ", timeit.default_timer() - starttime)

starttime = timeit.default_timer()
if re.search('|'.join(matches), haystack):
    print("Found with regex in ", timeit.default_timer() - starttime)


# After many trial runs, the regex continually came out much (much) faster: 

('Found with looping in ', 9.5367431640625e-07)
('Found with any() in ', 5.0067901611328125e-06)
('Found with regex in ', 0.0003647804260253906)

Use the any() function. There are many SO questions that show how to do it. — Barmar
– Barmar, Commented Jul 22, 2020 at 23:04
You can also turn matches into a regular expression, then check if the regexp matches. — Barmar
– Barmar, Commented Jul 22, 2020 at 23:06

Jab · Accepted Answer · 2020-07-22 23:19:08Z

3

Use re:

import re

matches = ["NEEDLE1", "NEEDLE2", "N33DL3"]
haystack = 'this is a haystack, there may or may not be a noodley needle around here. Needless to say I hate N33DL3 people'

if re.search('|'.join(matches), haystack):
    print("Found")

The '|' symbol means or in regex so you're looking for any of the words in matches using this search.

Edit

If you plan to use this search often I would compile the regex once globally or however then use the compiled version everywhere you need it instead of creating it over and over:

find_matches = re.compile('|'.join(matches))
#then where you need it:
if find_matches.search(haystack):
    ...

edited Jul 22, 2020 at 23:19

answered Jul 22, 2020 at 23:12

Jab

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3 Comments

Rino Bino Over a year ago

Thank you I would have never thought of this one on my own. I'll give this some testing before accepting but this looks fast and cheap which is great because my "real world" app has much larger matches and haystacks.

Rino Bino Over a year ago

By far this is much much faster than my original snippet and using any(match in haystack for match in matches): -- (a lot faster, I'll edit the OP with timings).

Jab Over a year ago

Your original snippet will print 'Found' for every time it finds a match. If you want this result use re.findall or re.finditer instead of re.search and it will return a list/iter of all matches instead of just that it found any amount of matches

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