bpo-38558: Link to further docs from walrus operator mention in tutorial

[adorilson]

This PR:

1. add versionchanged mark in walrus operation citation (to make explicited that this just works in 3.8 or later)
2. remove mentions to C language (we can't assume that everybody knows what is C)
3. add walrus operator example (example is always good)

https://bugs.python.org/issue38558

[ammaraskar]

add versionchanged mark in walrus operation citation (to make explicited that this just works in 3.8 or later)

I don't think an off-hand mention in the tutorial is a good spot for versionchanged, those usually go in the actual methods/declarations that were changed. In this case I think the whatsnew entry that mentions the walrus operator adequately covers when it was added.

remove mentions to C language (we can't assume that everybody knows what is C)

You don't have to know what C is to broadly understand the problem here, one can just ignore the parts mentioning C and still understand it. I think the comparison to a known language where this bug is common helps clarify the motivation for the existence of the walrus.

add walrus operator example (example is always good)

An example would be useful but I think some thought needs to be given to what would be useful in this context and not covered by the walrus operator's whatsnew entry (maybe a link to it should be added instead).

[zware]

Agreed with everything @ammaraskar mentioned. If anything is to be changed here, I think just a link to the docs for the walrus operator would be plenty.

[csabella]

@adorilson, please respond to the review comments.

[adorilson]

Hi, people.

I concord with some points, but not totally.

I'm OK about versionchanged, it was never used in tutorial. On the other hands, reference to whatsnew was not too (at least I don't found it). So in this point, is more consisted we link to PEP 572.

I think we need put some details about walrus operator in tutorial or at least a reference before datastructures chapter.

What's you think about first-steps-towards-programming section? It's look a good place for me. This section cite all the other operators used in conditions.

[JulienPalard]

I concur with @zware, please keep it simple, it's just a note, and it's just a tutorial.

Just link to https://docs.python.org/3/faq/design.html#why-can-t-i-use-an-assignment-in-an-expression which is the only part of the doc where we "document" the walrus (there's /reference/ but again it's a tutorial, it's not nice to send newcomers to read the reference).

[csabella]

@adorilson, I agree with @zware and @JulienPalard, where just adding a link would be best. The C language was mentioned in the prior version of this section. The change that added := here was just correcting a statement that was now untrue in that original note. Also, the intro to the tutorial says

This tutorial does not attempt to be comprehensive and cover every single feature, or even every commonly used feature. Instead, it introduces many of Python’s most noteworthy features, and will give you a good idea of the language’s flavor and style.

Based on that, I don't think it needs to be covered in detail. I checked the PEP for the discussions that had occurred around teaching this operator and didn't find anything there, but I seemed to recall that this operator was a more advanced concept that wouldn't need to be taught to beginners. I think it's OK to leave it out of the tutorial (except for correcting the original note), except, as others have suggested, adding a link to the note that was already added.

Thanks!

[adorilson]

Just link to https://docs.python.org/3/faq/design.html#why-can-t-i-use-an-assignment-in-an-expression

I reverted the previous commits and I done this.

[bedevere-bot]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

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[adorilson]

I have made the requested changes; please review again

[bedevere-bot]

Thanks for making the requested changes!

@zware: please review the changes made to this pull request.

Changes correctly applied.

[miss-islington]

Thanks @adorilson for the PR, and @JulienPalard for merging it 🌮🎉.. I'm working now to backport this PR to: 3.8.
🐍🍒⛏🤖

[bedevere-bot]

GH-18335 is a backport of this pull request to the 3.8 branch.

[JulienPalard]

Thanks @adorilson for this PR!