Finding all possible substrings within a string. Python Regex

Question

I want to find all possible substrings inside a string with the following requirement: The substring starts with N, the next letter is anything but P, and the next letter is S or T

With the test string "NNSTL", I would like to get as results "NNS" and "NST"

Is this possible with Regex?

Answer 1

Try the following regex:

N[^P\W\d_][ST]

The first character is N, the next character is none of (^) P, a non-letter (\W), a digit (\d) or underscore (_). The last letter is either S or T. I'm assuming the second character must be a letter.

EDIT

The above regex will only match the first instance in the string "NNSTL" because it will then start the next potential match at position 3: "TL". If you truly want both results at the same time use the following:

(?=(N[^P\W\d_][ST])).

The substring will be in group 1 instead of the whole pattern match which will only be the first character.