codelaw-rules-python
codelaw's rules for Python — one of the first-party rule packs
(SR-RULE-PACKS). It ships on
PyPI only, as codelaw-rules-python; npm has no copy (L6 decision 11).
# codelaw.toml
extends = ["codelaw:py/recommended"]
preview = true # every rule is `preview` until a corpus run promotes it
Presets
| preset | rules | ported from |
|---|---|---|
py/recommended |
97 | Ruff 0.17.1: its long-standing default E4, E7, E9, F (55 of 59 rules; the other four are below), all 39 stable flake8-bugbear B rules, isort's I001, RUF022 and py/use-instead (inert until replacements is set, W-73) |
py/conventions |
2 | opt-in house conventions from the starter catalogue: py/no-print, py/no-tunable-literals |
py/project |
1 | graph/no-unused-exports, the rule that reads the whole repo, from vulture's unused-function check — opt in |
py/size |
3 | size limits at warn: py/max-lines (1000 per module, Pylint's too-many-lines), py/max-lines-per-function (50) and py/max-params (5, Pylint's and Ruff's) — opt in |
The starter catalogue's other Python rules match a Ruff rule, so they sit in
py/recommended under their starter ids: py/no-bare-except (E722),
py/no-mutable-default (B006) and py/all-sorted (RUF022).
Every rule is reimplemented, not vendored: the matchers, messages and docs
are written fresh from Ruff's documented behaviour, and each rule's
ported_from: names the source rule. 101 rules are native: (Rust, in
crates/codelaw-native/src/python_*.rs); py/no-tunable-literals is a
match: rule.
Ported
| Ruff | rule | fix |
|---|---|---|
E401 |
py/multiple-imports-on-one-line |
auto |
E402 |
py/module-import-not-at-top |
manual |
E711 |
py/none-comparison |
suggest |
E712 |
py/true-false-comparison |
suggest |
E713 |
py/not-in-test |
auto |
E714 |
py/not-is-test |
auto |
E721 |
py/type-comparison |
manual |
E722 |
py/no-bare-except |
suggest |
E731 |
py/lambda-assignment |
suggest |
E741 |
py/ambiguous-variable-name |
manual |
E742 |
py/ambiguous-class-name |
manual |
E743 |
py/ambiguous-function-name |
manual |
F401 |
py/unused-import |
suggest |
F402 |
py/import-shadowed-by-loop-var |
manual |
F403 |
py/no-star-import |
manual |
F404 |
py/late-future-import |
manual |
F405 |
py/star-import-usage |
manual |
F406 |
py/nested-star-import |
manual |
F407 |
py/undefined-future-feature |
manual |
F501 |
py/percent-format-invalid |
manual |
F502 |
py/percent-format-expected-mapping |
manual |
F503 |
py/percent-format-expected-sequence |
manual |
F504 |
py/percent-format-unused-named-argument |
auto |
F505 |
py/percent-format-missing-argument |
manual |
F506 |
py/percent-format-mixed-placeholders |
manual |
F507 |
py/percent-format-count-mismatch |
manual |
F508 |
py/percent-format-star-requires-sequence |
manual |
F509 |
py/percent-format-unsupported-character |
manual |
F521 |
py/format-invalid |
manual |
F522 |
py/format-unused-named-argument |
auto |
F523 |
py/format-unused-positional-argument |
auto |
F524 |
py/format-missing-argument |
manual |
F525 |
py/format-mixed-numbering |
manual |
F541 |
py/f-string-missing-placeholders |
auto |
F601 |
py/duplicate-dict-key |
manual |
F602 |
py/duplicate-dict-key-variable |
manual |
F621 |
py/too-many-expressions-in-star-assignment |
manual |
F622 |
py/multiple-starred-expressions |
manual |
F631 |
py/assert-tuple |
manual |
F632 |
py/is-literal |
suggest |
F633 |
py/invalid-print-syntax |
manual |
F634 |
py/if-tuple |
manual |
F701 |
py/break-outside-loop |
manual |
F702 |
py/continue-outside-loop |
manual |
F704 |
py/yield-outside-function |
manual |
F706 |
py/return-outside-function |
manual |
F707 |
py/default-except-not-last |
manual |
F722 |
py/forward-annotation-syntax-error |
manual |
F811 |
py/redefined-while-unused |
manual |
F821 |
py/undefined-name |
manual |
F822 |
py/undefined-export |
manual |
F823 |
py/undefined-local |
manual |
F841 |
py/unused-variable |
suggest |
F842 |
py/unused-annotation |
auto |
F901 |
py/raise-not-implemented |
suggest |
B002 |
py/unary-prefix-increment |
manual |
B003 |
py/assignment-to-os-environ |
manual |
B004 |
py/unreliable-callable-check |
suggest |
B005 |
py/strip-with-multi-characters |
manual |
B006 |
py/no-mutable-default |
suggest |
B007 |
py/unused-loop-control-variable |
suggest |
B008 |
py/function-call-in-default-argument |
manual |
B009 |
py/getattr-with-constant |
auto |
B010 |
py/setattr-with-constant |
auto |
B011 |
py/assert-false |
suggest |
B012 |
py/jump-statement-in-finally |
manual |
B013 |
py/redundant-tuple-in-exception-handler |
auto |
B014 |
py/duplicate-handler-exception |
auto |
B015 |
py/useless-comparison |
manual |
B016 |
py/raise-literal |
manual |
B017 |
py/assert-raises-exception |
manual |
B018 |
py/useless-expression |
manual |
B019 |
py/cached-instance-method |
manual |
B020 |
py/loop-variable-overrides-iterator |
manual |
B021 |
py/f-string-docstring |
manual |
B022 |
py/useless-contextlib-suppress |
manual |
B023 |
py/function-uses-loop-variable |
manual |
B024 |
py/abstract-base-class-without-abstract-method |
manual |
B025 |
py/duplicate-try-block-exception |
manual |
B026 |
py/star-arg-unpacking-after-keyword-arg |
manual |
B027 |
py/empty-method-without-abstract-decorator |
manual |
B028 |
py/no-explicit-stacklevel |
suggest |
B029 |
py/except-with-empty-tuple |
manual |
B030 |
py/except-with-non-exception-classes |
manual |
B031 |
py/reuse-of-groupby-generator |
manual |
B032 |
py/unintentional-type-annotation |
manual |
B033 |
py/duplicate-set-value |
auto |
B034 |
py/re-sub-positional-args |
manual |
B035 |
py/static-key-dict-comprehension |
manual |
B039 |
py/mutable-contextvar-default |
manual |
B904 |
py/raise-without-from-inside-except |
manual |
B905 |
py/zip-without-explicit-strict |
suggest |
B911 |
py/batched-without-explicit-strict |
suggest |
B912 |
py/map-without-explicit-strict |
suggest |
I001 |
py/unsorted-imports |
auto |
RUF022 |
py/all-sorted |
auto |
How the ports differ
Every rule matches Ruff's documented behaviour on Ruff's own examples. Where
codelaw differs, the rule's ## Differences from the source section says so.
The ones that shape results most:
| area | difference |
|---|---|
| name resolution | The semantic model is per scope, not per statement: a name bound anywhere in a scope counts as bound everywhere in it, and del is not tracked. Ruff follows the order statements run in, so it reports a few more F821, F405, F811 and F401 findings in code that rebinds names conditionally. |
py/redefined-while-unused |
A read anywhere between two definitions counts as a use, even inside a function body that only runs later, and so does a mention in a string annotation; as in Ruff, a redefinition in a different branch (if __name__ == "__main__":) is not reported; a parameter shadowing a module-level import is not reported. |
py/unused-import |
Names in string annotations, and in strings inside typing generics (Dict["Name", int]), cast() and TypeVar(bound=), count as uses; # type: comments don't, as in Ruff 0.17. Not reported for imports in a class body, import a.b loading a submodule of a package also imported under an alias, or importing __all__ (Ruff reports that one). Imports inside a try body are reported without an edit. The fix is suggest, because an import can run code. |
py/unused-variable |
As in Ruff, unpacking is reported only from a tuple or list literal. Outside functions only an unused except … as name is reported. |
py/unsorted-imports |
Checks order only. Blank lines after the import block and line wrapping are the formatter's; from m import a, b as c and import a, b are not reported for their shape. First-party modules come from the known_first_party option. |
py/no-star-import |
Relative star imports (from .sub import *) are not reported: that is how a package re-exports its submodules. |
py/zip-without-explicit-strict, py/batched-without-explicit-strict, py/map-without-explicit-strict |
The Python version comes from each rule's target_version option, not a project setting; unset, the rules run. The fix adds strict=False, which keeps today's behaviour (Ruff has no fix for B911); it is suggest, not auto, because with the version unknown the keyword may not exist and would raise TypeError (W-17). |
py/no-mutable-default |
The fix is offered for unannotated parameters whose default doesn't read the parameter's own name. |
# noqa |
Ruff's suppression comments are not read; codelaw has its own. |
Not ported, and why
| rule | why |
|---|---|
pycodestyle E1, E2, E3, E5, W |
never: layout, which the formatter owns |
E701, E702, E703 |
never: layout (statements per line, semicolons) |
E902 io-error |
the engine reports files it can't read (codelaw/not-utf8, codelaw/internal-error) |
E999 syntax-error |
removed upstream in Ruff 0.8.0 |
B043, B901, B903, B909 |
preview-only in Ruff 0.17.1, not part of its stable B set |
flake8-bugbear B950 |
never: line length is layout, and Ruff doesn't implement it |
I002 missing-required-import |
needs the project's list of required imports; not part of I001 |
The rest of Ruff 0.16's wider default (UP, SIM, PL, C4, …) is planned
for a later py/strict preset (B-048 in work/BACKLOG.md).
Data
data/python/stdlib.json — the standard library's top-level module names, the
union of CPython 3.10–3.14's sys.stdlib_module_names, so modules removed in
recent versions (distutils, asynchat, imp, …) still count as standard
library. py/unsorted-imports uses it to place imports in sections. See
NOTICE.
Corpus check
Each run checks every rule and compares it line by line with Ruff 0.17.1
running the same rules (--select E4,E7,E9,F,B,I001,RUF022).
| corpus | files | findings | rules where codelaw and Ruff differ, and why |
|---|---|---|---|
CPython 3.9 standard library (lib/python3.9, no tests) |
420 | 1,526 | I001 (blank lines after imports, left to the formatter), F821/F405/F811/F401/F841 (Ruff follows statement order and del; codelaw doesn't report from io import __all__), F401/I001 # noqa lines, B028 (a warnings name with a None fallback), B012 (codelaw reports every return in a finally), B024 (class ABC inside abc.py), B912 (target_version unset) |
pip 21.2.4 pip/_internal |
141 | 310 | F401: 12 lines, every one marked # noqa; B912 (target_version unset) |
| rich 15.0.0 (fully annotated) | 100 | 98 | I001: 5 blocks missing only a blank line between sections; F401 and B007: one # noqa line each |
Applying every auto and suggest fix to all three corpora changed 368 files,
broke none, and left no fixable finding behind.
1 maintainer
Metadata
1 maintainer
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