gh-148488: Clarify the company/tag separator in the py -V docs

[serhiy-storchaka]

• Issue: Confusing documentation for "py -V" #148488

[read-the-docs-community]

Documentation build overview

📚 cpython-previews | 🛠️ Build #33515458 | 📁 Comparing c5efd35 against main (cd9994e)

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4 files changed

± library/tkinter.html
± library/tkinter.ttk.html
± using/windows.html
± whatsnew/changelog.html

[zooba]

The second part about the tag is not true - it's a fairly complicated comparison, but for equality it's actually a numeric-field-aware comparison against a list of possibilities provided by the runtime, tried first with the platform appended and then without.

So a runtime that provides ["3.14.6-amd64","3.14-amd64", "3-amd64"] should match 03.0014 because the number fields are compared numerically¹, but 3.1 will not match 3.14 even though it's a prefix. If you pass 3.14-amd64 then it first searches for 3.14-amd64-amd64 and won't find it, then it looks for 3.14-amd64, and because of ordering it'll match 3.14.6 before 3.14.5, so both can offer the same shortened version.

All that is way too complicated for right here, which is why I didn't want to put it in. It belongs in a new section about "how to create your own package feed". I can't come up with a suitable short way to introduce the concept that most well-defined packages will let you abbreviate a tag that is shaped like a version number, but if it doesn't work then check the feed. If you've got a brief way to put that here, let's see it, but otherwise I'd keep this paragraph about *company* and not mention tag other than to show the separator.

Footnotes

1. Something like (int('3'), '.', int('14'), '-amd64') == (int('03'), '.', int('0014'), '-amd64') plus it assumes base-10. It's possible that string components allow prefix matching - I don't remember right now. ↩