i am trying to do a multiple match within a lookbehind and a look forward
Let's say i have the following string:
$ Hi, this is an example @
Regex: (?<=$).+a.+(?=@)
I am expecting it to return both 'a' within those boundaries, is there a way to do it with only one regex?
Engine: Python
If you can use quantifiers in the lookbehind, use
(?<=\$[^$@]*?)a(?=[^@]*@)
See proof.
Explanation
--------------------------------------------------------------------------------
(?<= look behind to see if there is:
--------------------------------------------------------------------------------
\$ '$'
--------------------------------------------------------------------------------
[^$@]*? any character except: '$' and '@' (0 or more
times (matching the least amount possible))
--------------------------------------------------------------------------------
) end of look-behind
--------------------------------------------------------------------------------
a 'a'
--------------------------------------------------------------------------------
(?= look ahead to see if there is:
--------------------------------------------------------------------------------
[^@]* any character except: '@' (0 or more
times (matching the most amount
possible))
--------------------------------------------------------------------------------
@ '@'
--------------------------------------------------------------------------------
) end of look-ahead
PCRE pattern:
(?:\G(?<!^)|\$)[^$]*?\Ka(?=[^@]*@)
See another proof
Explanation
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(?: group, but do not capture:
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\G where the last m//g left off
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(?<! look behind to see if there is not:
--------------------------------------------------------------------------------
^ the beginning of the string
--------------------------------------------------------------------------------
) end of look-behind
--------------------------------------------------------------------------------
| OR
--------------------------------------------------------------------------------
\$ '$'
--------------------------------------------------------------------------------
) end of grouping
--------------------------------------------------------------------------------
[^$@]*? any character except: '$' and '@' (0 or more times
(matching the least amount possible))
--------------------------------------------------------------------------------
\K match reset operator
--------------------------------------------------------------------------------
a 'a'
--------------------------------------------------------------------------------
(?= look ahead to see if there is:
--------------------------------------------------------------------------------
[^@]* any character except: '@' (0 or more
times (matching the most amount
possible))
--------------------------------------------------------------------------------
@ '@'
--------------------------------------------------------------------------------
) end of look-ahead