Regex to match first and last word of a sentence only

Question

I am trying to match a sentence that starts with "hello" and ends with "bye". For example, "hello something bye" should result in a match.

I tried using the regular expression ^hello|[a-z]|bye$, but it detects everything. I have also tried googling, but I couldn't find a solution for this exact case.

@TimBiegeleisen I am looking for regex which will match for hello ________________ ____ __ ________ ______ ____ bye — , Apr 28 '23 at 12:14
As your question is not entirely clear, could you please confirm whether you intend to conduct a search for all the sentences that begin with "hello" and end with "bye", as you mentioned in your last comment? — Andreas Violaris, Apr 28 '23 at 12:46
"_hello something bye_" is not a sentence - it misses punctuation at the end. Just like your entire text in the question. Without that you have/want a phrase. — AmigoJack, Apr 28 '23 at 12:49

ABR · Answer 1 · 2023-04-28T12:19:35.430

1

^hello\b.*\bbye$

Explanation:

^ matches the start of the string (sentence)
hello matches the literal word "hello"
.* matches any character (except for newline) zero or more times
\b matches a word boundary (to ensure that "bye" is a whole word, not just a substring)
bye matches the literal word "bye"
$ matches the end of the string (sentence)

edited Apr 28 '23 at 12:19

answered Apr 28 '23 at 12:14

ABR

134
5

That's a good point. It's added. – ABR Apr 28 '23 at 12:18

score 1 · Answer 2 · answered Apr 28 '23 at 12:16

Generally speaking, you could use the regex pattern ^\w+|\w+$, which would only match words at the beginning or end. Assuming your actual language be Python, we can try:

inp = "hello something bye"
matches = re.findall(r'^\w+|\w+$', inp)
print(matches)  # ['hello', 'bye']

score 1 · Answer 3 · answered Apr 28 '23 at 12:34

Based on your comments, it seems that you want to match all instances of the specified pattern. In order to achieve this, you can use something like this:

import re

text = "irrelevant sentence hello first sentence bye irrelevant sentence hello second sentence bye " \
       "irrelevant sentence hello third sentence bye irrelevant sentence"

regex = r"(?:^|\s)(hello\s.*?bye)(?=\s|$)"

matches = re.findall(regex, text)

if matches:
    print("Matches found:", matches)
else:
    print("Matches not found.")

Output:

Matches found: ['hello first sentence bye', 'hello second sentence bye', 'hello third sentence bye']

Regex to match first and last word of a sentence only

3 Answers3