Rules

Rattle’s built-in rules are grouped by collection. Enable a collection by adding its name to enable, or enable a single rule by its kebab-case name.

Blank Lines

Whitespace and statement-separation rules.

Enable with:

enable = ["blank-lines"]

Rule	Message	Python	Autofix
blank-line-after-control-block	Add a blank line after this multiline control-flow block.	Any	Yes
blank-line-after-terminal-control-block	Add a blank line after this early-exit control-flow block.	Any	Yes
blank-line-before-branch	Add a blank line before this branch statement in a larger code block.	Any	Yes
blank-line-before-unrelated-block	Add a blank line before this block; the preceding statements do not prepare values used by it.	Any	Yes
no-suite-leading-trailing-blank-lines	Remove blank lines at the beginning or end of a code block.	Any	Yes

Exports

Rules for explicit module export surfaces.

Enable with:

enable = ["exports"]

Rule	Message	Python	Autofix
module-all-at-bottom	Define module __all__ at the bottom of the file.	Any	Yes
no-underscore-all-exports	Do not export underscore-prefixed symbols in __all__. Either remove them from __all__ or rename them to be public.	Any	No

Policy

Configurable policy rules for architecture and naming boundaries.

Enable with:

enable = ["policy"]

Rule	Message	Python	Autofix
forbidden-call	Do not call forbidden callable ‘{symbol}’.	Any	No
forbidden-import	Do not import across forbidden boundary ‘{boundary}’.	Any	No
forbidden-name	Do not use forbidden {kind} name ‘{name}’.	Any	No
line-count-limit	{target} has {actual_lines} lines, exceeding the configured limit of {max_lines}.	Any	No
no-relative-imports	Use absolute imports instead of relative imports.	Any	No
no-underscore-import-aliases	Import aliases must not start with an underscore.	Any	No
no-unsafe-tempfile-factories	Use tempfile context managers instead of mkstemp or mkdtemp.	Any	No

Style

Rules for code style and structure.

Enable with:

enable = ["style"]

Rule	Message	Python	Autofix
no-annotated-self	Do not annotate self in instance methods.	Any	Yes
no-exception-message-variables	Inline exception message strings instead of assigning throwaway variables.	Any	Yes
no-str-exception-translation	Use a fixed message when translating an exception, and preserve the cause with raise ... from exc.	Any	No
no-underscore-class	Class names must not start with an underscore prefix.	Any	No
public-method-order	Define public methods before underscore-prefixed helper methods.	Any	No

Typing

Rules for type annotations and modern typing syntax.

Enable with:

enable = ["typing"]

Rule	Message	Python	Autofix
no-bare-object-annotations	Replace this bare object annotation with a type that describes the value.	Any	No

Fixit

Core lint rules inherited from Fixit.

Enable with:

enable = ["fixit"]

Rule	Message	Python	Autofix
explicit-frozen-dataclass	Dataclass mutability must be explicit. Add frozen=True for immutable value objects or frozen=False when instances are intentionally mutable.	Any	No
no-named-tuple	NamedTuple can often be replaced with @dataclass, but dataclasses are not tuple-compatible; check callers before converting.	Any	No
no-static-if-condition	This if condition appears constant; verify the logic and remove any temporary debug clause.	Any	No
sorted-attributes	Class assignments under @sorted-attributes are not sorted; sorting them can change right-hand-side side-effect order.	Any	Yes
use-callable-ellipsis	Use Callable[…, T] instead of Callable[[…], T].	Any	Yes
use-rattle-ignore-comment	Use rattle: ignore[rule-name]; Rattle does not support noqa.	Any	No
use-types-from-typing	Python 3.8 does not support {builtin_type}[...] annotations; use typing.{correct_type} instead.	< 3.9	Yes

Fixit Extra

Additional Fixit-derived rules that can be enabled separately.

Enable with:

enable = ["fixit-extra"]

Rule	Message	Python	Autofix
collapse-isinstance-checks	Multiple isinstance calls with the same target but different types can be collapsed into a single call with a tuple of types.	Any	No
deprecated-unittest-asserts	{deprecated} is deprecated; use {replacement} instead.	Any	Yes
no-inherit-from-object	Remove the redundant object base class.	Any	Yes
no-or-in-except	Use except (ValueError, TypeError):; except ValueError or TypeError: catches only ValueError.	Any	No
no-redundant-arguments-super	Call super() without arguments.	Any	No
no-redundant-f-string	Remove the f prefix; this f-string has no replacement fields.	Any	Yes
no-redundant-lambda	The lambda that wraps {function} is redundant and can be replaced by the callable.	Any	No
no-redundant-list-comprehension	Unnecessary list comprehension inside {func}(). Use a generator expression instead.	Any	No
no-string-type-annotation	Remove the quotes from this annotation; postponed evaluation is already enabled.	Any	Yes
replace-union-with-optional	Optional[T] is preferred over Union[T, None] or Union[None, T].	Any	No
use-assert-equal	Use assertEqual() or assertNotEqual() instead of wrapping an equality comparison in assertTrue().	Any	Yes
use-assert-in	Use assertIn() or assertNotIn() for membership checks.	Any	Yes
use-assert-is-not-none	Use assertIsNone() or assertIsNotNone() for None checks.	Any	Yes
use-async-sleep-in-async-def	Do not call blocking time.sleep inside async functions; use asyncio.sleep or an async runtime sleep.	Any	No
use-cls-in-classmethod	When using @classmethod, the first argument must be cls.	Any	Yes
use-collections-abc	Import abstract base classes from collections.abc.	>= 3.3	Yes
use-comprehension	Replace this {func}() call with the equivalent comprehension.	Any	No
use-eq-for-primitives	Use == or != for numeric and string values; is tests object identity.	Any	Yes
use-f-string	Use an f-string instead of % formatting or str.format().	Any	Yes
use-is-for-singletons	Compare None, True, and False with is or is not.	Any	Yes
use-literal	Replace this {func}() call with the equivalent collection literal.	Any	Yes