Regular Expressions 101

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"
(?<!\S)INT.EST.C.S.(?!\S)
"
g
Negative Lookbehind
(?<!\S)
Assert that the Regex below does not match
\S matches any non-whitespace character (equivalent to [^\r\n\t\f\v ])
INT
matches the characters INT literally (case sensitive)
. matches any character (except for line terminators)
EST
matches the characters EST literally (case sensitive)
. matches any character (except for line terminators)
C matches the character C with index 6710 (4316 or 1038) literally (case sensitive)
. matches any character (except for line terminators)
S matches the character S with index 8310 (5316 or 1238) literally (case sensitive)
. matches any character (except for line terminators)
Negative Lookahead
(?!\S)
Assert that the Regex below does not match
\S matches any non-whitespace character (equivalent to [^\r\n\t\f\v ])
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