Python regex error: “cannot refer to an open group”









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I am creating rules for a reddit automoderator. It gets its rules from a YAML config file and the regexes are interpreted as Python regex.



I am trying to make the following regular expression work:



(https?://[\w\d:#@%/;$()~_?+-=\.&]+\.\w2,6)([\S\s]*\1)


When I test it on https://pythex.org/ it works perfectly to achieve what I want.



Unfortunately my group reference at the end of the expression is causing an error when I copy the same regex into the config file:




Generated an invalid regex for body (regex): cannot refer to an open
group




I have also tried this version with everything escaped just to make sure that the characters weren't interfering in any way:



(https?://[\w\d\:\#\@\%\/\;\$\(\)\~\_\?\+\-\=\.&]+\.\w2,6)([\S\s]*\1)


But I still get the same error. Does anyone know what I'm doing wrong here?










share|improve this question























  • Can you try to print the regex? Also, try it without the ( [Ss]* 1 ) and see if it errors.
    – sln
    Nov 11 at 19:23










  • I cannot print the regex, as I am just setting rules in YAML and they are being interpreted by someone else's python code. It does not have errors without the end group.
    – Patrick Thorpe
    Nov 11 at 19:28










  • That error is thrown if you reference a group inside the group like this so it could be the closing ) is not being seen.
    – sln
    Nov 11 at 19:29










  • Then, remove the end group and just put 1 at the end, as a test.
    – sln
    Nov 11 at 19:30











  • And, it wouldn't hurt to escape the forward slashes for a test ((https?://[wd:#@%/;$()~_?+-=.&]+.w2,6)([Ss]*1) Note that you have to escape the dash in the class if you want it to be literal -
    – sln
    Nov 11 at 19:34















up vote
-1
down vote

favorite












I am creating rules for a reddit automoderator. It gets its rules from a YAML config file and the regexes are interpreted as Python regex.



I am trying to make the following regular expression work:



(https?://[\w\d:#@%/;$()~_?+-=\.&]+\.\w2,6)([\S\s]*\1)


When I test it on https://pythex.org/ it works perfectly to achieve what I want.



Unfortunately my group reference at the end of the expression is causing an error when I copy the same regex into the config file:




Generated an invalid regex for body (regex): cannot refer to an open
group




I have also tried this version with everything escaped just to make sure that the characters weren't interfering in any way:



(https?://[\w\d\:\#\@\%\/\;\$\(\)\~\_\?\+\-\=\.&]+\.\w2,6)([\S\s]*\1)


But I still get the same error. Does anyone know what I'm doing wrong here?










share|improve this question























  • Can you try to print the regex? Also, try it without the ( [Ss]* 1 ) and see if it errors.
    – sln
    Nov 11 at 19:23










  • I cannot print the regex, as I am just setting rules in YAML and they are being interpreted by someone else's python code. It does not have errors without the end group.
    – Patrick Thorpe
    Nov 11 at 19:28










  • That error is thrown if you reference a group inside the group like this so it could be the closing ) is not being seen.
    – sln
    Nov 11 at 19:29










  • Then, remove the end group and just put 1 at the end, as a test.
    – sln
    Nov 11 at 19:30











  • And, it wouldn't hurt to escape the forward slashes for a test ((https?://[wd:#@%/;$()~_?+-=.&]+.w2,6)([Ss]*1) Note that you have to escape the dash in the class if you want it to be literal -
    – sln
    Nov 11 at 19:34













up vote
-1
down vote

favorite









up vote
-1
down vote

favorite











I am creating rules for a reddit automoderator. It gets its rules from a YAML config file and the regexes are interpreted as Python regex.



I am trying to make the following regular expression work:



(https?://[\w\d:#@%/;$()~_?+-=\.&]+\.\w2,6)([\S\s]*\1)


When I test it on https://pythex.org/ it works perfectly to achieve what I want.



Unfortunately my group reference at the end of the expression is causing an error when I copy the same regex into the config file:




Generated an invalid regex for body (regex): cannot refer to an open
group




I have also tried this version with everything escaped just to make sure that the characters weren't interfering in any way:



(https?://[\w\d\:\#\@\%\/\;\$\(\)\~\_\?\+\-\=\.&]+\.\w2,6)([\S\s]*\1)


But I still get the same error. Does anyone know what I'm doing wrong here?










share|improve this question















I am creating rules for a reddit automoderator. It gets its rules from a YAML config file and the regexes are interpreted as Python regex.



I am trying to make the following regular expression work:



(https?://[\w\d:#@%/;$()~_?+-=\.&]+\.\w2,6)([\S\s]*\1)


When I test it on https://pythex.org/ it works perfectly to achieve what I want.



Unfortunately my group reference at the end of the expression is causing an error when I copy the same regex into the config file:




Generated an invalid regex for body (regex): cannot refer to an open
group




I have also tried this version with everything escaped just to make sure that the characters weren't interfering in any way:



(https?://[\w\d\:\#\@\%\/\;\$\(\)\~\_\?\+\-\=\.&]+\.\w2,6)([\S\s]*\1)


But I still get the same error. Does anyone know what I'm doing wrong here?







regex regex-group






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share|improve this question













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edited Nov 12 at 7:28









Anthon

28.2k1693144




28.2k1693144










asked Nov 11 at 19:13









Patrick Thorpe

6411




6411











  • Can you try to print the regex? Also, try it without the ( [Ss]* 1 ) and see if it errors.
    – sln
    Nov 11 at 19:23










  • I cannot print the regex, as I am just setting rules in YAML and they are being interpreted by someone else's python code. It does not have errors without the end group.
    – Patrick Thorpe
    Nov 11 at 19:28










  • That error is thrown if you reference a group inside the group like this so it could be the closing ) is not being seen.
    – sln
    Nov 11 at 19:29










  • Then, remove the end group and just put 1 at the end, as a test.
    – sln
    Nov 11 at 19:30











  • And, it wouldn't hurt to escape the forward slashes for a test ((https?://[wd:#@%/;$()~_?+-=.&]+.w2,6)([Ss]*1) Note that you have to escape the dash in the class if you want it to be literal -
    – sln
    Nov 11 at 19:34

















  • Can you try to print the regex? Also, try it without the ( [Ss]* 1 ) and see if it errors.
    – sln
    Nov 11 at 19:23










  • I cannot print the regex, as I am just setting rules in YAML and they are being interpreted by someone else's python code. It does not have errors without the end group.
    – Patrick Thorpe
    Nov 11 at 19:28










  • That error is thrown if you reference a group inside the group like this so it could be the closing ) is not being seen.
    – sln
    Nov 11 at 19:29










  • Then, remove the end group and just put 1 at the end, as a test.
    – sln
    Nov 11 at 19:30











  • And, it wouldn't hurt to escape the forward slashes for a test ((https?://[wd:#@%/;$()~_?+-=.&]+.w2,6)([Ss]*1) Note that you have to escape the dash in the class if you want it to be literal -
    – sln
    Nov 11 at 19:34
















Can you try to print the regex? Also, try it without the ( [Ss]* 1 ) and see if it errors.
– sln
Nov 11 at 19:23




Can you try to print the regex? Also, try it without the ( [Ss]* 1 ) and see if it errors.
– sln
Nov 11 at 19:23












I cannot print the regex, as I am just setting rules in YAML and they are being interpreted by someone else's python code. It does not have errors without the end group.
– Patrick Thorpe
Nov 11 at 19:28




I cannot print the regex, as I am just setting rules in YAML and they are being interpreted by someone else's python code. It does not have errors without the end group.
– Patrick Thorpe
Nov 11 at 19:28












That error is thrown if you reference a group inside the group like this so it could be the closing ) is not being seen.
– sln
Nov 11 at 19:29




That error is thrown if you reference a group inside the group like this so it could be the closing ) is not being seen.
– sln
Nov 11 at 19:29












Then, remove the end group and just put 1 at the end, as a test.
– sln
Nov 11 at 19:30





Then, remove the end group and just put 1 at the end, as a test.
– sln
Nov 11 at 19:30













And, it wouldn't hurt to escape the forward slashes for a test ((https?://[wd:#@%/;$()~_?+-=.&]+.w2,6)([Ss]*1) Note that you have to escape the dash in the class if you want it to be literal -
– sln
Nov 11 at 19:34





And, it wouldn't hurt to escape the forward slashes for a test ((https?://[wd:#@%/;$()~_?+-=.&]+.w2,6)([Ss]*1) Note that you have to escape the dash in the class if you want it to be literal -
– sln
Nov 11 at 19:34













1 Answer
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down vote



accepted










I managed to fix the problem by changing the group selection to 2 instead of 1.



It turned out that YAML or AutoModerator were automatically putting parentheses around the whole expression, so any group references within must be 1 more than you would initially expect.



I had thought that this was the problem at the start, and tried the fix explained above, however due to a separate issue with the AutoModerator code, the fix had not appeared to have worked. All resolved now though; thanks for your patience and help.






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    1 Answer
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    active

    oldest

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    oldest

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    active

    oldest

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    up vote
    0
    down vote



    accepted










    I managed to fix the problem by changing the group selection to 2 instead of 1.



    It turned out that YAML or AutoModerator were automatically putting parentheses around the whole expression, so any group references within must be 1 more than you would initially expect.



    I had thought that this was the problem at the start, and tried the fix explained above, however due to a separate issue with the AutoModerator code, the fix had not appeared to have worked. All resolved now though; thanks for your patience and help.






    share|improve this answer
























      up vote
      0
      down vote



      accepted










      I managed to fix the problem by changing the group selection to 2 instead of 1.



      It turned out that YAML or AutoModerator were automatically putting parentheses around the whole expression, so any group references within must be 1 more than you would initially expect.



      I had thought that this was the problem at the start, and tried the fix explained above, however due to a separate issue with the AutoModerator code, the fix had not appeared to have worked. All resolved now though; thanks for your patience and help.






      share|improve this answer






















        up vote
        0
        down vote



        accepted







        up vote
        0
        down vote



        accepted






        I managed to fix the problem by changing the group selection to 2 instead of 1.



        It turned out that YAML or AutoModerator were automatically putting parentheses around the whole expression, so any group references within must be 1 more than you would initially expect.



        I had thought that this was the problem at the start, and tried the fix explained above, however due to a separate issue with the AutoModerator code, the fix had not appeared to have worked. All resolved now though; thanks for your patience and help.






        share|improve this answer












        I managed to fix the problem by changing the group selection to 2 instead of 1.



        It turned out that YAML or AutoModerator were automatically putting parentheses around the whole expression, so any group references within must be 1 more than you would initially expect.



        I had thought that this was the problem at the start, and tried the fix explained above, however due to a separate issue with the AutoModerator code, the fix had not appeared to have worked. All resolved now though; thanks for your patience and help.







        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered Nov 11 at 20:27









        Patrick Thorpe

        6411




        6411



























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