Regular Expressions 101

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'
^(?!["#\n])(.*?)=(.*?)([#].*)?$
'
gm
^ asserts position at start of a line
Negative Lookahead
(?!["#\n])
Assert that the Regex below does not match
Match a single character present in the list below
["#\n]
"#
matches a single character in the list "# (case sensitive)
\n matches a line-feed (newline) character (ASCII 10)
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 6110 (3D16 or 758) 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)
3rd Capturing Group
([#].*)?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
Match a single character present in the list below
[#]
# matches the character # with index 3510 (2316 or 438) 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

Substitution

Processing...