{"action":"closed","issue":{"url":"https://api.github.com/repos/ipython/traitlets/issues/256","repository_url":"https://api.github.com/repos/ipython/traitlets","labels_url":"https://api.github.com/repos/ipython/traitlets/issues/256/labels{/name}","comments_url":"https://api.github.com/repos/ipython/traitlets/issues/256/comments","events_url":"https://api.github.com/repos/ipython/traitlets/issues/256/events","html_url":"https://github.com/ipython/traitlets/issues/256","id":164662701,"number":256,"title":"how to extend dynamic defaults with super","user":{"login":"minrk","id":151929,"avatar_url":"https://avatars.githubusercontent.com/u/151929?v=3","gravatar_id":"","url":"https://api.github.com/users/minrk","html_url":"https://github.com/minrk","followers_url":"https://api.github.com/users/minrk/followers","following_url":"https://api.github.com/users/minrk/following{/other_user}","gists_url":"https://api.github.com/users/minrk/gists{/gist_id}","starred_url":"https://api.github.com/users/minrk/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/minrk/subscriptions","organizations_url":"https://api.github.com/users/minrk/orgs","repos_url":"https://api.github.com/users/minrk/repos","events_url":"https://api.github.com/users/minrk/events{/privacy}","received_events_url":"https://api.github.com/users/minrk/received_events","type":"User","site_admin":false},"labels":[],"state":"closed","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":9,"created_at":"2016-07-09T11:16:03Z","updated_at":"2016-11-01T12:58:59Z","closed_at":"2016-11-01T12:58:59Z","body":"With traitlets 4.0, it's easy to extend dynamic defaults of parent classes, because the name of the default generator is part of the public API:\n\n``` python\nclass SubClass(Parent):\n    def _some_trait_default(self):\n        previous_default = super()._trait_default()\n        return modified(previous_default)\n```\n\nNow that the name of the method that happens to implement the default generator is no longer a public API, what's the best way to determine what the dynamic default _would have been_ in the parent class, and then extend it in a subclass?\n"}}
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