Match a string which is succeeded by a character but don't match the character itself in regex

Question

I have a string
"a_c d_"
I want to just be able to match the letters using regex that are immediately succeeded by `_`. For example, "a" & "d".

I tried using the pattern `\w_`, but it matches the letter as well as the underscore. So the returned values are "a_" & "d_".

But I just want to have "a" & "d". How can I do that?

Answer 1

XXX , lookahead pattern is what you need. Look at the code. Hope it helps you.
https://code.sololearn.com/WaeK72RAIoRu/?ref=app

Answer 2

𝐊𝐢𝐢𝐛𝐨 𝐆𝐡𝐚𝐲𝐚𝐥 quoted from the question

`I tried using the pattern '\w_', but it matches the letter as well as the underscore. So the returned values are "a_" & "d_"`

I know the guidelines.

EDIT: made the question clearer by separating into paragraphs