Regular Expressions 101

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"
(.*?)@(.*?)\.(.{2,3})
"
g
1st Capturing Group
(.*?)
.
matches any character (except for line terminators)
*? matches the previous token between zero and unlimited times, as few times as possible, expanding as needed (lazy)
@ matches the character @ with index 6410 (4016 or 1008) literally (case sensitive)
2nd Capturing Group
(.*?)
.
matches any character (except for line terminators)
*? matches the previous token between zero and unlimited times, as few times as possible, expanding as needed (lazy)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
3rd Capturing Group
(.{2,3})
.
matches any character (except for line terminators)
{2,3} matches the previous token between 2 and 3 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)
Your regular expression does not match the subject string.

Regular Expression
No Match

r"
"
g

Test String