Message 316186 - Python tracker

Message316186

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Author	terry.reedy
Recipients	docs@python, hongweipeng, terry.reedy
Date	2018-05-04.21:42:38
SpamBayes Score	-1.0
Marked as misclassified	Yes
Message-id	<1525470158.97.0.682650639539.issue33417@psf.upfronthosting.co.za>
In-reply-to

Content
https://docs.python.org/3/reference/datamodel.html#customizing-instance-and-subclass-checks says "Note that these methods are looked up on the type (metaclass) of a class. They cannot be defined as class methods in the actual class. This is consistent with the lookup of special methods that are called on instances, only in this case the instance is itself a class." IE, your first example is documented as wrong. Your second example, which works, follows the example in https://docs.python.org/3/reference/datamodel.html#customizing-instance-and-subclass-checks

Content

https://docs.python.org/3/reference/datamodel.html#customizing-instance-and-subclass-checks
says
"Note that these methods are looked up on the type (metaclass) of a class. They cannot be defined as class methods in the actual class. This is consistent with the lookup of special methods that are called on instances, only in this case the instance is itself a class."

IE, your first example is documented as wrong.  Your second example, which works, follows the example in
https://docs.python.org/3/reference/datamodel.html#customizing-instance-and-subclass-checks

History
Date	User	Action	Args
2018-05-04 21:42:38	terry.reedy	set	recipients: + terry.reedy, docs@python, hongweipeng
2018-05-04 21:42:38	terry.reedy	set	messageid: <1525470158.97.0.682650639539.issue33417@psf.upfronthosting.co.za>
2018-05-04 21:42:38	terry.reedy	link	issue33417 messages
2018-05-04 21:42:38	terry.reedy	create