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Chat GPT 4 - testing regular expression generation

Tue, 28 Mar 2023 by garethbrown

This was a quick test of Chat GPT 4's performance on a simple regular expression task I had coded manually earlier in the day where I needed to extract the text from a connection string property "Application Name" in a PostgreSQL connection string.

Seeing this Hacker News post regarding a service called, I decided to see how Chat GPT 4 might have performed. In this case at least, I think Chat GPT has performed amazingly. I had earlier manually coded the regex (Application\sName=)([^;]+), which fitted my use case well.

Chat GPT responded with (?<=Application Name=)[^;]+. This solution works (as tested at It doesn't allow for the capture of the value for the Application Name property but then I didn't ask it to. I'm especially impressed with its ability to explain the pattern.



Testing another generalised simple use case, giving the following prompt to Chat GPT 4 where we look to extract all property names from the connection string:

Write a regular expression to extract the property names from this PostgreSQL connection string: "PostgresSql": "Host=localhost;User ID=postgres;Password=xxxx;Database=test;Application Name=Test1234,Port=35432;Pooling=false;"

Yields the response with an explanation:

(?<=[^\\w])([A-Za-z ]+)(?==)

"This regular expression will match any sequence of alphabetic characters (upper or lower case) that are followed by an equal sign (=). The negative lookbehind (?<=[^\w]) ensures that the property name is not preceded by another word character."


A quick test on shows this works perfectly.

I think that Chat GPT at version 4 has become a truly useful tool.

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