Ruff v0.16.0

Ruff v0.16.0 now enables 413 rules by default, up from 59 in previous versions, according to an announcement from Brent Westbrook. The update, which expands the total rule count from 708 to 968, catches severe issues including syntax errors and immediate runtime errors without requiring configuration. Simon Willison reported that running the tool against his projects Datasette, sqlite-utils, and LLM found hundreds of minor issues, with sqlite-utils alone showing 1,618 errors (1,538 fixed, 80 remaining) after applying fixes.

"ruff" dev dependency. From Brent Westbrook's announcement post: Ruff now enables 413 rules by default, up from 59 in previous versions. Since Ruff's default rule set was last modified in v0.1.0 , the number of rules in Ruff has grown from 708 to 968. Many of these rules catch severe issues, including syntax errors and immediate runtime errors but were not previously enabled by default. With the new rule set, Ruff will bring these issues and many others to your attention without any Ruff configuration. Here's a one-liner for trying it on any Python project: uvx ruff@latest check . I ran the latest Ruff against my three biggest projects - Datasette https://datasette.io/ , sqlite-utils https://sqlite-utils.datasette.io/ , and LLM https://llm.datasette.io/ - and it found hundreds of minor issues that breached the new default rules. All three projects have very comprehensive test suites, executed in CI against Python 3.10 through Python 3.14, so upgrades like this are pretty safe. The following command did the bulk of the upgrades: uvx ruff@latest check . --fix --unsafe-fixes Against sqlite-utils , that command reported: Found 1618 errors 1538 fixed, 80 remaining . As an illustrative example, here are three of the remaining issues. Ruff does a nice job of explaining each one: php DTZ005 datetime.datetime.now called without a tz argument -- tests/test duplicate.py:17:10 | 15 | "datetime col" TEXT """ 16 | Insert one row of mock data: 17 | dt = datetime.datetime.now | ^^^^^^^^^^^^^^^^^^^^^^^ 18 | data = { 19 | "text col": "Cleo", | help: Pass a datetime.timezone object to the tz parameter BLE001 Do not catch blind exception: Exception -- tests/test plugins.py:16:12 | 14 | db.execute "select from pragma function list " 15 | return True 16 | except Exception: | ^^^^^^^^^ 17 | return False 18 | finally: | B018 Found useless attribute access. Either assign it to a variable or remove it. -- tests/test update.py:46:5 | 44 | def test update invalid pk fresh db, pk, update pk : 45 | table = fresh db "table" 46 | table.insert {"id1": 5, "id2": 3, "v": 1}, pk=pk .last pk | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 47 | with pytest.raises NotFoundError : 48 | table.update update pk, {"v": 2} | Unsurprisingly, given Astral's new home at OpenAI https://simonwillison.net/2026/Mar/19/openai-acquiring-astral/ , this output provides everything a coding agent would need to fix the problems. I had Codex GPT-5.6 Sol high upgrade LLM https://github.com/simonw/llm/pull/1557 and sqlite-utils https://github.com/simonw/sqlite-utils/pull/814 , and Claude Code with Opus 5 upgrade Datasette https://github.com/simonw/datasette/pull/2857 .