Difference between regex and re library

[alvations]

Would regex be faster? Or more stable?

Would changing from re to regex break the existing rules?

[BLKSerene]

I'm not an expert of regular expression or Python's 3rd-party library regex, but there's some general comments:

1. AFAIK, no performance comparison between re and regex has been officially documented by the author of regex, but I suppose that since regex implements more functions, it should be slower than re, but I'm not sure whether or not the difference in speed is significant. (cf. Issue #282)
   One special case: if there's something regex can do but re cannot, and the code can be greatly simplified, then there might be a non-trivial improvement in speed. e.g. look-behinds in re must be fixed-width, but regex allows non-fixed-width look-behinds.
2. re is part of Python's standard library and regex is a 3rd-party library, so updates on re is only released when a new version of Python is released and releases of regex can be made more frequently. So I suppose that re is more stable than regex, though that also means new features (including performance optimizations) will be added to re slower than regex (but in your case new features are not your concerns, I suppose).
3. Changing from re to regex is not supposed to break the existing rules, as regex "is backwards-compatible with the standard ‘re’ module, but offers additional functionality" (https://pypi.org/project/regex/)

[goodmami]

From my limited experience using regex, I don't think there's a lot to gain unless you really need greater (but still not full) PCRE compatibility. I don't believe there's any noticeable performance difference (but I haven't benchmarked them). The developer of regex runs Windows only and seems to be uninterested in doing anything to better support Linux or MacOS (I hope I'm not taking this out of context; here's the thread). Also, if you use the library for better PCRE compatibility (i.e., using the V1 flag), then some warnings will become errors (here's where I encountered the same thing).