René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Improved performance and arguably simpler code for dictionaries by changing the keys layout","articleBody":"### Current layout\n\nCurrently the `_dictkeysobject` struct is laid out like this:\n```\nptr ----\u003e  +--------------+\n           |     header   |\n           +--------------+\n           |    indices   |\n           +--------------+\n           |     keys     |\n           +--------------+\n```\nwhich requires some relatively expensive calculation to find the start of the keys, as the indices are not only variable in number, but variable in size also.\n\n### Proposed layout\nIf instead it is laid out as follows:\n```\n           +--------------+\n           |    indices   |\nptr ----\u003e  +--------------+\n           |     header   |\n           +--------------+\n           |     keys     |\n           +--------------+\n```\nand the indices laid from highest to lowest with 0 just before `ptr`, finding the start of the keys is as simple as `ptr-\u003ekeys` . Accessing an index is no slower, and the code barely any more complex.\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-145097\n* gh-150640\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/markshannon","@type":"Person","name":"markshannon"},"datePublished":"2025-12-17T15:58:54.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/142889/cpython/issues/142889"}