René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Make inspect.Parameter.__hash__ use _default instead of default","articleBody":"# Feature or enhancement\r\n\r\nEnable subclasses of Parameter to add a `default` property accessing hash(self) rather than having hash rely on the `default` property\r\n\r\n# Pitch\r\n\r\nI wanted to make a subclass of Parameter which would store as _default the string eval-ing to the actual default value, and which would only eval it when accessed, and memorize it at that time.\r\nSo, I coded this :\r\n```py\r\nclass Parameter(inspect.Parameter):\r\n    __slots__ = ()\r\n    @property\r\n    @functools.cache\r\n    def default(self):\r\n        return renpy.python.py_eval(super(Parameter, self).default)\r\n```\r\n(not using @cached_property because I want to keep the empty slots)\r\nThis doesn't work, because `cache` tries to hash `self`, and Parameter.\\_\\_hash\\_\\_ accesses `self.default`, rather than `self._default` (so it does an infinite recursion loop).\r\n\r\nThe last edit to the hash method was purportedly to \"fix a discrepancy between eq and hash\". However, the eq still accesses the raw _default, and hash did so too before the \"fix\".\r\nOverall, apart from my selfish use-case, I think it makes more sense for an immutable class to hash relative to the actual value instead of the less-reliable propertied value.\r\nAnd there's a minor performance bonus too.\r\n\r\n\u003c!-- gh-linked-prs --\u003e\r\n### Linked PRs\r\n* gh-102303\r\n\u003c!-- /gh-linked-prs --\u003e\r\n","author":{"url":"https://github.com/Gouvernathor","@type":"Person","name":"Gouvernathor"},"datePublished":"2023-02-27T15:52:06.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":13},"url":"https://github.com/102302/cpython/issues/102302"}