gh-106780: Add __match_args__ to tutorial example

[terryjreedy]

Add Point definition with this attribute before example that needs it.

• Issue: docs.python.org | 4.6. match Statements #106780

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📚 Documentation preview 📚: https://cpython-previews--106784.org.readthedocs.build/

[methane]

How about using dataclass or namedtuple with comment?

[terryjreedy]

@methane Class Point without the added line appears at line 309 followed by a match statement whose cases only use keyword matching. The paragraph that follow mentions using match_args to allow cases using positional matching. This augmented class and the match that follows illustrates this point. Without this, using the previous definition of Point, this example fails. So I consider this the proper fix for this issue. Note that the primary purpose of this example is to show nested patterns, in this case class(es) inside of a sequence. Showing positional matching is secondary.

This is the tutorial and to me, namedtuples and dataclasses are a more advanced topic. (I have never used the latter.) I think they should be another issue.

[miss-islington]

Thanks @terryjreedy for the PR 🌮🎉.. I'm working now to backport this PR to: 3.11, 3.12.
🐍🍒⛏🤖

[bedevere-bot]

GH-106819 is a backport of this pull request to the 3.12 branch.

[bedevere-bot]

GH-106820 is a backport of this pull request to the 3.11 branch.

[methane]

The paragraph that follow mentions using match_args to allow cases using positional matching. This augmented class and the match that follows illustrates this point.

Both of dataclasses and __match_args__ are mentioned:

 You can use positional parameters with some builtin classes that provide an
 ordering for their attributes (e.g. dataclasses). You can also define a specific
 position for attributes in patterns by setting the ``__match_args__`` special
 attribute in your classes.

This is the tutorial and to me, namedtuples and dataclasses are a more advanced topic. (I have never used the latter.) I think they should be another issue.

I feel manually define __match_args__ is more advanced than just using dataclass.
I used dataclasses, namedtuples, and similar objects many times. But I never write __matcch_args__ manually except testing match statement behavior.

Anyway, it is a matter of preference and either is acceptable.