[Python-Dev] Re: pre-PEP: Complete, Structured Regular Expression Group Matching (original) (raw)

Erik Heneryd erik at heneryd.com
Tue Aug 10 14:57:10 CEST 2004

Mike Coleman wrote:

Paul Moore <pfmoore at yahoo.co.uk> writes:

The only other comment I have is that the semantics seem pretty complex - I think that in practice, they do more or less what you want them to, but the description is pretty obscure.

I'd say that is probably a warning flag, but I don't know, at the same time it looks like it could be kind of useful.

And although I can see that the error return has some value, I suspect that it might actually complicate real use.

Someone else suggested throwing an exception instead, which I'm now leaning in favor of, too.

Exceptions are the way to go. You should get what you ask for, or a heads up. Errors should never pass silently.

A suggestion - would it be possible to implement re.structmatch as a pure Python prototype, to thrash out some of the usability questions? If the function appears valuable in such a form, arguing for incorporation into the re module would be a lot easier. I suspect that in this case a pure Python implementation might actually be a lot harder than implementing it as a C patch. This is because so much of the work is already done in the current re module; the C patch would probably not be that big. In order to do it in Python I'd end up reimplementing re.match in Python, which I wouldn't look forward to.

I hacked up a Python prototype, mostly as a challenge. It's brittle and it's ugly, but it kind of works. Though, if /F says it would require a major rewrite of the C-engine, that's probably true...

Erik

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