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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Panic in csv.writer with QUOTE_STRINGS or QUOTE_NOTNULL","articleBody":"## Summary\n\n`csv.writer` panics when `quoting` is set to `csv.QUOTE_STRINGS` or\n`csv.QUOTE_NOTNULL`.\n\nBoth constants are exposed by RustPython, but the writer path still reaches a\n`todo!()` implementation for these quote styles.\n\n## Reproducer\n\n```python\nimport csv\nimport io\n\nbuf = io.StringIO()\ncsv.writer(buf, quoting=csv.QUOTE_STRINGS).writerow([\"x\", 1, None, \"\"])\nprint(repr(buf.getvalue()))\n\nbuf = io.StringIO()\ncsv.writer(buf, quoting=csv.QUOTE_NOTNULL).writerow([\"x\", 1, None, \"\"])\nprint(repr(buf.getvalue()))\n```\n\n## Expected\n\nCPython exits normally and produces:\n\n```text\n'\"x\",1,,\"\"\\r\\n'\n'\"x\",\"1\",,\"\"\\r\\n'\n```\n\n`QUOTE_STRINGS` quotes fields whose original value is a string, while `None`\nis written as an empty unquoted field.\n\n`QUOTE_NOTNULL` quotes every field except `None`, which is written as an empty\nunquoted field.\n\nA single empty field produced from `None` should raise `csv.Error`:\n\n```python\ncsv.writer(io.StringIO(), quoting=csv.QUOTE_STRINGS).writerow([None])\ncsv.writer(io.StringIO(), quoting=csv.QUOTE_NOTNULL).writerow([None])\n```\n\n## Actual\n\nRustPython panics with:\n\n```text\nthread 'main' panicked at crates/stdlib/src/csv.rs:...:\nnot yet implemented\n```\n\nThe panic comes from the `QuoteStyle::Strings` / `QuoteStyle::Notnull` mapping\ninside the native `_csv` implementation.\n\n## Python Documentation\n\n`csv.QUOTE_STRINGS` and `csv.QUOTE_NOTNULL` are documented quoting constants:\n\nhttps://docs.python.org/3/library/csv.html#csv.QUOTE_STRINGS\nhttps://docs.python.org/3/library/csv.html#csv.QUOTE_NOTNULL\n","author":{"url":"https://github.com/doma17","@type":"Person","name":"doma17"},"datePublished":"2026-06-15T10:37:18.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/8108/RustPython/issues/8108"}