Regular Expressions 101

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"
(?s)(\#\d{1,})(.*?)(\#\d{1,})
"
gm
(?s)
match the remainder of the pattern with the following effective flags: gms
s modifier: single line. Dot matches newline characters
1st Capturing Group
(\#\d{1,})
\# matches the character # with index 3510 (2316 or 438) literally (case sensitive)
\d
matches a digit (equivalent to [0-9])
{1,} matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
2nd Capturing Group
(.*?)
.
matches any character
*? matches the previous token between zero and unlimited times, as few times as possible, expanding as needed (lazy)
3rd Capturing Group
(\#\d{1,})
\# matches the character # with index 3510 (2316 or 438) literally (case sensitive)
\d
matches a digit (equivalent to [0-9])
{1,} matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
Global pattern flags
g modifier: global. All matches (don't return after first match)
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
Your regular expression does not match the subject string.

Regular Expression
No Match

r"
"
gm

Test String