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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Remove `DELETE_FAST` bytecode instruction","articleBody":"`DELETE_FAST` has two uses:\n1. `delete var` where `var` is a local variable\n2. Cleaning up at the end of a named exception block.\n\nA local variable can be deleted with the sequence `PUSH_NULL; STORE_FAST var`.\n\n#### Deleting a local variable\n\nInstead of `DELETE_FAST n` we can emit `LOAD_FAST n; POP_TOP n; PUSH_NULL; STORE_FAST n` which the bytecode optimizer will reduce to `PUSH_NULL; STORE_FAST n` in most cases.\n\n#### Cleaning up at the end of a named exception block.\n\nWe currently emit the sequence: `LOAD_CONST None; STORE_FAST n; DELETE_FAST n`\nwhich can be replaced with `PUSH_NULL; STORE_FAST n`\n\nThis case is far more common than explicitly deleting a local variable, so we can reduce code size as well as freeing up an opcode.\n\n---------------------------------\n\nSee https://github.com/faster-cpython/ideas/issues/490\n\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-145983\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/markshannon","@type":"Person","name":"markshannon"},"datePublished":"2026-03-10T14:02:10.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":5},"url":"https://github.com/145749/cpython/issues/145749"}