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regexregexp-replace

How can I use regular expressions to insert commas into large integers?

I have a text document with a lot of large integers, e.g. 123456789. I want to automatically insert commas into these to make them more readable: 123,456,789. However, my document also contains decimals, and these should remain untouched. Is there a regular expressions that will insert these? An answer on a similar question suggested (?<=\d)(?=(\d\d\d)+(?!\d)), but this also detects decimal numbers. What's more, I am unable to insert the commas using either Notepad++ or Overleaf. What should I replace this regex with?

Solution

  • My guess is that maybe, 

    (?<=\d)(?=(?:\d{3})+(?!\d|\.))

    or 

    (?!^)(?=(?:\d{3})+(?!\.|\d))

    Demo 2

    or

    \d+\.\d*(*SKIP)(*FAIL)|(?!^)(?=(?:\d{3})+(?!\.|\d))

    Demo 3

    might be close to what you're trying to write, which you can simply replace it with a comma.

    If you wish to simplify/modify/explore the expression, it's been explained on the top right panel of regex101.com. If you'd like, you can also watch in this link, how it would match against some sample inputs.