Regular Expressions 101

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"
^([2-3])\.([1-9])\.([1-9])
"
gm
^ asserts position at start of a line
1st Capturing Group
([2-3])
Match a single character present in the list below
[2-3]
2-3 matches a single character in the range between 2 (index 50) and 3 (index 51) (case sensitive)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
2nd Capturing Group
([1-9])
Match a single character present in the list below
[1-9]
1-9 matches a single character in the range between 1 (index 49) and 9 (index 57) (case sensitive)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
3rd Capturing Group
([1-9])
Match a single character present in the list below
[1-9]
1-9 matches a single character in the range between 1 (index 49) and 9 (index 57) (case sensitive)
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