Using VB.NET, I have created an AddIn for Autodesk Inventor and the customer has a bunch of drawing number strings which follow this sort of scheme:

  1. P01867-13-TP09-001-4950-1775-1175-895-1125-835
  2. P01867-13-TP09-002-4950-1775-1045-895-1035
  3. P01867-13-TP02-019-L-1137-275-852-102
  4. P01867-13-TP02-019-L-1137-275-852-102
  5. P01867-13-TP02-019-R-1137-275-852-102
  6. P01867-13-TP02-021-L-1137-1055-1372
  7. P01867-13-TP02-021-L-1137-535-1027
  8. P01867-13-TP02-021-L-1137-795-1184
  9. P01867-13-TP02-021-R-1137-1055-1372
  10. P01867-13-TP02-021-R-1137-535-1027
  11. P01867-13-TP02-021-R-1137-795-1184
  12. P01867-13-TP02-025-L-1137-1315-1581
  13. P01867-13-TP02-025-R-1137-1315-1581
  14. P01867-13-TP03-005
  15. P01867-13-TP02-019-L-1137-275
  16. P01867-13-TP02-019-R-1137-275
  17. P01867-13-TP02-019-R-1137
  18. P01867-13-TP02-019-L-1137

In order to account for these groups of three digits within the variations I have created the following regex:


I now have to add the capability of looking for a sixth group of digits so figured I would ask here if there is a method within regex (which I may have overlooked) that will allow me to improve upon/simplify the above monster.


1 Answer 1



Your current regex is WAY too forgiving. First of all, every one of your example starts with a P followed by some numbers, but you accept ANY COMBINATION of letters at the beginning. I'm assuming that ALEX01867-13-TP02-019-L-1137 isn't a valid key, so you should take steps to reject it by using hungry quantifiers as little as possible (*, +). Using \d{3,4} matches a digit between 3 and 4 times, so that will let you limit the sort of input you accept.

The same goes for the 5th group - according to your examples, it's either L, R, or 4 digits. In Regex, that looks like this: (L|R|\d{4})

Next, you are using alternation (option1|option2) to capture the different "forms" your string comes in as, but you are repeating a bunch of stuff (for example, the \w*\d* at the beginning). You can limit the scope of the alternation by surrounding it in brackets (()). You can see this in action with the (L|R|\d{4}) example - that whole bracket group becomes a single token that matches somewhere in a string (or doesn't).

Sometimes the string ends after the 4th group (Before the L/R group), and sometimes it doesn't. Instead of using alternation to solve this, which makes the regex VERY long, you can just surround the entire regex AFTER that point in brackets with a question mark (an-(example)?). This makes the entire second part optional.

Finally, your problem asks if there is a simple method to improve the regex. By ending it in (-\d{3,4})* you can match ANY length of additions to the end, assuming the all come in the form -015 or -1992 or whatever. If you knew that there was always a max of 15 numbers added to the end, you could change that star (*) to a max quantifier ({,15}). If sometimes the number only has two digits, change the {3,4} to {2,4}, etc.

See it in action here

  • \$\begingroup\$ Thanks for the explanation/solution @devon-parsons! I do need to group each of the three-digit strings into groups in order to be able to retrieve Dimension A, B, C, D etc. from the strings that continue after the L or R values - does that make sense? \$\endgroup\$ Oct 16, 2015 at 13:15
  • \$\begingroup\$ With repeated groups, you can only capture the final group that gets captured - so currently, your first line would capture -835. If you need ALL of them, you can capture EVERYTHING after the L/R by putting brackets around it and using your programming language of choice to split on the - characters to get the different groups. \$\endgroup\$ Oct 16, 2015 at 14:06
  • \$\begingroup\$ To be clear, that means you would surround (-\d{3,4})* with brackets to make the entire string read ^P\d{5}-13-TP\d{2}-\d{3}(-(L|R|\d{4})((-\d{3,4})*))?$. One of the capture groups will look like -001-002-003-004 etc. if you feel like it, look up non-capturing groups (?:) to tidy it up. \$\endgroup\$ Oct 16, 2015 at 14:10
  • 1
    \$\begingroup\$ So I have cobbled together this: (?'DrawingNumber'^P\d{5}-\d{2}-TP\d{2}-\d{3})-?(?'Hand'L|R)?-?(?'Dimensions'(-?\d{2,})*)-?(?'Type'1|2)?$ based on your suggestions which looks like it can account for the Drawing Number, Hand (if one exists), the Dimensions if applicable and lastly a type (1 or 2) if applicable - regex101.com/r/eF3hC1/2 - Thanks again! \$\endgroup\$ Oct 16, 2015 at 14:50

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