Regular Expressions 101

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"
^x(\d+)($|:.*$)
"
gm
^ asserts position at start of a line
x matches the character x with index 12010 (7816 or 1708) literally (case sensitive)
1st Capturing Group
(\d+)
\d
matches a digit (equivalent to [0-9])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
2nd Capturing Group
($|:.*$)
1st Alternative
$
$ asserts position at the end of a line
2nd Alternative
:.*$
: matches the character : with index 5810 (3A16 or 728) literally (case sensitive)
.
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

Regular Expressions 101

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