On Wed, Oct 21, 2020 at 10:22 AM Steven D'Aprano <steve@pearwood.info> wrote:
Well... yes. And oddly enough, developing a scanning mini-language inspired by the formatting language is *exactly* what this proposal is, and has always been.
That's incorrect.
The first post in this thread:
https://mail.python.org/archives/list/python-ideas@python.org/thread/JEGSKOD...
literally describes it as f-strings as the target. There's no hint that only a subset of f-string functionality will be accepted. Dennis says:
"you can assign a string to an f-string"
and proposes an exception:
"ValueError: f-string assignment target does not match ..."
The first post was just talking about the syntactic concept, without any explanation of how an f-string match pattern would work. Once we got to actual concrete proposals, they were always about a scanning mini-language inspired by the formatting language. I'm really not sure what you're arguing here.
I think we have at least six mini-languages now?
- regexes - string interpolation with % - template strings - format mini-language - f-strings - date/time format strings
I think it would be quite an uphill battle to have a seventh built into the language. You're welcome to write a PEP :-)
If you're going to count date/time format strings, you should also count logging formats, and a ton of other things around the place. Mini-languages aren't a problem. They're just a compact form of structured data (or code, depending on your context). What's the issue here? Remember, this is *closely related to* an existing one, meaning that it won't have the cognitive load of a complete new system. ChrisA