[issue9212] dict_keys purports to implement the Set ABC, but is missing the isdisjoint method

Raymond Hettinger report at bugs.python.org
Sun Jul 11 00:08:13 CEST 2010

Raymond Hettinger <rhettinger at users.sourceforge.net> added the comment:

Concrete classes are allowed to have more features than the corresponding ABC.  The ABCs are not intended to be full-featured; instead, they specify the part of the API that will be guaranteed.  For example, the union() method for built-in sets allows two or more set arguments, but the corresponding method for the ABC is limited to two arguments.  This was an intentional difference, designed to make it easier for people to implement a Set class.

That being said, the omission of isdisjoint() was an oversight and I see no reason that this shouldn't be fixed.

nosy: +rhettinger

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