Regular Expressions 101

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"
^(\d\d\d\d-\d\d-\d\dT\d\d:\d\d:\d\d\.\d\d\d\d\d\d-\d\d:\d\d) (.*?) (.*?): (.*)$
"
gm
^ asserts position at start of a line
1st Capturing Group
(\d\d\d\d-\d\d-\d\dT\d\d:\d\d:\d\d\.\d\d\d\d\d\d-\d\d:\d\d)
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
T matches the character T with index 8410 (5416 or 1248) literally (case sensitive)
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
: matches the character : with index 5810 (3A16 or 728) literally (case sensitive)
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
: matches the character : with index 5810 (3A16 or 728) literally (case sensitive)
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
: matches the character : with index 5810 (3A16 or 728) literally (case sensitive)
\d matches a digit (equivalent to [0-9])
\d matches a digit (equivalent to [0-9])
matches the character with index 3210 (2016 or 408) 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 3210 (2016 or 408) literally (case sensitive)
3rd 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 characters : literally (case sensitive)
4th Capturing Group
(.*)
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
$ asserts position at the end of a line
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