Regular Expressions 101

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"
\b(?:[0-9]{1,3}\.){3}[0-9]{1,3}\b
"
g
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
Non-capturing group
(?:[0-9]{1,3}\.){3}
{3} matches the previous token exactly 3 times
Match a single character present in the list below
[0-9]
{1,3} matches the previous token between 1 and 3 times, as many times as possible, giving back as needed (greedy)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
Match a single character present in the list below
[0-9]
{1,3} matches the previous token between 1 and 3 times, as many times as possible, giving back as needed (greedy)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case sensitive)
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
Global pattern flags
g modifier: global. All matches (don't return after first match)
Your regular expression does not match the subject string.

Regular Expression
No Match

r"
"
g

Test String