gh-143535: Document dispatch behavior of singledispatchmethod by priyanshu2282-cyber · Pull Request #143592 · python/cpython · GitHub

The PR clarifies the behavior of singledispatchmethod in the documentation. It always dispatches the first argument during call, regardless of whether the method is bound or unbound, as a result xf(a)!=c.f(x,a). The behavior is intentional and required to support correct dispatch for staticmethod and classmethod.

Issue: singledispatchmethod dispatches on first argument to instance-bindable method called from class level #143535

📚 Documentation preview 📚: https://cpython-previews--143592.org.readthedocs.build/

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Co-authored-by: Bartosz Sławecki <bartosz@ilikepython.com>

Align your paragraph with the other paragraphs, that is, use the correct indentation. You're 1 space off.

Got it, Aligned!

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.

You don't define a singledispatchmethod, you decorate one with this decorator. See the other paragraphs.

You don't define a singledispatchmethod

It doesn't say singledispatchmethod defined in a class, but singledispatchmethod method defined in a class.

However, I agree that the current wording can be better. If it was good, you wouldn't have raised the thread.

Thanks for your clarification, I have used the decorators as suggested, and updated the PR.

I have made the requested changes; please review again

Thanks for making the requested changes!

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

You did not address all my comments. I am going offline but I really need you to address everything before requesting a review as this makes me lose my time.

Sorry for the back-and-forth. I’ve addressed all the review comments and also I have made the requested changes; please review again @picnixz

Hi @johnslavik, just checking in on this PR in case it slipped through. No rush at all, would appreciate your feedback when you have time. Thanks!

#144615 demonstrates that this behavior can be fairly easily accounted for. I'd prefer to elevate the capability rather than document the deficiency.

Agreed. Let us close this one then.

pythongh-143535 : Document dispatch behavior of singledispatchmethod

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priyanshu2282-cyber requested a review from rhettinger as a code owner January 9, 2026 09:50

bedevere-app Bot added docs Documentation in the Doc dir skip news labels Jan 9, 2026

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singledispatchmethod dispatches on first argument to instance-bindable method called from class level #143535

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github-project-automation Bot moved this to Todo in Docs PRs Jan 9, 2026

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priyanshu2282-cyber added 2 commits January 9, 2026 15:42

pythongh-143535 : Move singledispatchmethod note outside example block

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Merge branch 'main' into doc-singledispatchmethod-dispatch

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pythongh-143535 : Clarify dispatch semantics of singledispatchmethod

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bedevere-app Bot requested a review from picnixz January 9, 2026 11:12

johnslavik reviewed Jan 12, 2026

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priyanshu2282-cyber and others added 2 commits January 12, 2026 20:41

Update Doc/library/functools.rst

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Co-authored-by: Bartosz Sławecki <bartosz@ilikepython.com>

Indentation fixes

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priyanshu2282-cyber requested a review from johnslavik January 13, 2026 14:29

picnixz requested changes Jan 13, 2026

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pythongh-143535 : Fix indentation in singledispatchmethod docs

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bedevere-app Bot requested a review from picnixz January 13, 2026 18:13

Used decorators

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picnixz closed this Feb 16, 2026

+                  For every ``singledispatchmethod`` method defined in a class, the value
+                  dispatched on by that method is *always* the first argument passed for the call.
+                  Therefore, dispatching to regular methods can only be sensibly performed by
+                  calling such a method from instances of the class, and not from the class object.

                  The same pattern can be used for other similar decorators:
                  :deco:`staticmethod`, :deco:`~abc.abstractmethod`, and others.
+                  For every ``singledispatchmethod`` method defined in a class, the value

gh-143535: Document dispatch behavior of singledispatchmethod by priyanshu2282-cyber · Pull Request #143592 · python/cpython · GitHub

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gh-143535: Document dispatch behavior of singledispatchmethod - #143592

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