René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"`.pyc` files are larger than they need to be","articleBody":"Python 3.11 made `.pyc` files almost twice as large. There are two main reasons for this:\r\n- [PEP 659](https://peps.python.org/pep-0659/) made the bytecode stream ~3x as large as 3.10.\r\n- [PEP 657](https://peps.python.org/pep-0657/) made the location tables ~9x as large as 3.10.\r\n\r\n(Note that these effects compound each other, since longer bytecode means more location entries.)\r\n\r\nHowever, there is low-hanging fruit for improving this situation in 3.12:\r\n- Bytecode can be compressed using a fairly simple scheme (one byte for instructions without an oparg, two bytes for instructions with an oparg, and zero bytes for `CACHE` entries). **This results in serialized bytecode that is ~66% smaller than 3.11.**\r\n- The location table format already has a mechanism for compressing multiple code units into a single entry. Currently it's only used for `EXTENDED_ARG`s and `CACHE`s corresponding to a single instruction, but with slight changes the compiler can use the same mechanism to share location table entries between adjacent instructions. This is a double-win, since it not only makes `.pyc` files smaller, but also shrinks the memory footprint of all code objects in the process. **Experiments show that this makes location tables ~33% smaller than 3.11.**\r\n\r\nWhen both of these optimizations are applied, `.pyc` files become ~33% smaller than 3.11. This is only ~33% larger than 3.10, despite all of the rich new debugging information present.\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-99555\n* gh-99556\n* gh-100435\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/brandtbucher","@type":"Person","name":"brandtbucher"},"datePublished":"2022-11-17T00:15:51.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/99554/cpython/issues/99554"}