Python regex pattern: find single “o” letters (multiple o-s should be excluded)

Question

['xxoxoxoxoxoxooxxxxox\n', 'xxxxxxxxxxxxxxxxooox\n', 'xoxoxoxoxoxoxoxoxoxo\n', 'ooxoxoxoxoxoxoxooxox\n', 'xxxxxxxxxxxxxxxxoooo\n', 'xxxxxxxxxxxxxxxxxxxx\n', 'oooooooooooooooooooo\n', 'xxxxxxxxxxooxxxxxxxx\n', 'xooxxxxxxxxxoxxxxxoo\n', 'xxxxxxoxxxxxxxoxxooo\n', 'xooooooooxoooooooxxx\n', 'ooooooxoxoxoxoxoxoxo\n', 'oxxxxxxxxxxxxxxxxxoo\n', 'xxxxxxxxxxxxooooooox\n', 'oxxxxxxxxxxxxxoooooo\n']

Imagine that this string is a theater where you have to find all free single seats.

x = seats sold out
o = seats free

With “free single seat” I mean seats that

(1) has no free neighbors (no multiple “o”-s) and

(2) not located at the beginning or end of a row (as eg. in the last line).

I tried the following RegEx pattern:

[^o]o[^o]

Does not work because it can’t find all single “o”, eg. in “xoxoxox” it misses the second “o”.

Any idea for solution?

Answer 1

okay...
(?<=x)o(?=x)
maybe.. its using lookahead and lookbehind to make sure it has x around it

it works in js, it should works too in python
const x = [...'xoxoxoxox'.matchAll(/(?<=x)o(?=x)/g)]

i tested it again with oxoxoox its only return 1 o.

Answer 2

Taste Thanks!
Your code helped me, I didn’t know these lookahead and lookbehind tricks.
Actually, I had to extend it because line start and end was not recognized.

This works perfectly:

((?<=\')|(?<=x))(o)((?=x)|(?=\\))

Answer 3

good to know

Answer 4

why not just o+ ?
or just o if you only need to find every single o seperately

Answer 5

Taste
I have added more details to my question, eg. multiple “o”-s are not allowed.