Regex to Capture and wrap outline formatted text - regex

Question

I have source text that is not particularly clean or well formed but I have a need to find text and wrap a line in a tag. The text is in outline format.
1. becomes a <h1> tag
A. becomes a <h2> tag
(1) becomes a <h3> tag
and so on...
Here are some examples of the source.
PREPARE FOR TEST A. Open the door. B. Turn on the light.
The desired result would be
<h1>1. PREPARE FOR TEST</h1>
<h2>A. Open the door.</h2>
<h2>B. Turn on the light.</h2>
Unfortunately, the text could be the same line or it could be on multiple lines or even have a different number of spaces between the outline number and the text. Another example
(1) Check air inlet and air outlet valves are shown open if OAT is above > 53.6 deg F., or closed if OAT is below
48.2 deg F.
In this case the desired result would be
<h3>(1) Check skin air inlet and skin air outlet valves are shown open if temperature is above 53.6 deg F., or closed if temperature is below 48.2 deg F.</h3>
My questions are
How do I find an entire line of text that is associated with an outline level, i.e., the 1., A., (1) and so on.
How do I then wrap that text with the appropriate tag.
I'm not particularly strong at regex, I have been able to do some of the simpler things required of this project but this has me stumped a bit. Here's what I used to try to find the H1 lines, but as anyone that knows regex can plainly see, this won't work past the first word.
\d{1,3}.\s+[A-Z]{2,}
I'm using Python at the moment but am better with PHP and can move to that if needed and still may because I'm better at PHP then Python.
Thank you.

Answer 1

Since every regex needs a different substitution, you need to apply each regex in turn. Assuming that you want the match to always span an entire line, I'd suggest something like this:
import re
s = """1. becomes a h1 tag
A. becomes a h2 tag
(1) becomes a h3 tag
and so on..."""
regexes = {r"\d+\.": "h1",
r"[A-Z]+\.": "h2",
r"\(\d+\)": "h3",
}
for regex in regexes:
repl = regexes[regex]
s = re.sub("(?m)^" + regex + ".*", "<" + repl + ">" + r"\g<0>" + "</" + repl + ">", s)
print(s)
Result:
<h1>1. becomes a h1 tag</h1>
<h2>A. becomes a h2 tag</h2>
<h3>(1) becomes a h3 tag</h3>
and so on...
Explanation:
Each of the regexes (which only match the actual identifiers) is modified to match from the start of the line until the end of the line:
"(?m)^" + regex + ".*" # (?m) allows ^ to match at the start of lines
The entire match is contained in group 0 which can be accessed in the replacement string via \g<0>.
"<" + repl + ">" + r"\g<0>" + "</" + repl + ">" # add tags around line

Answer 2

For future reference and to close this, what I eventually came up with was to run through the entire string of text and remove some trash first. There are actually 15 of these that I use for this step.
$regexes['lf'] = "/[\n\r]*/";
$regexes['tab-cr-lf'] = "/\t[\r\n]/";
preg_replace($regexes,"", $string);
I then discovered that I could count on space and \t after each header identifier, so then I run some more regexes on the string
$regexes['step1'] = "/(\d{1,2}\..\t)/";
$regexes['step2'] = "/([A-Z]\. \t)/";
$replacements['step1'] = "\n\n<step1>$0";
$replacements['step2'] = "\n\n<step2>$0";
preg_replace($this->headerRegexes, $replacements, $string);
These steps have given me some usable text that I can work with.
Thanks to everyone that chimed in, it gave me somethings to think about as I tackled this problem.