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	Missing blank line after multiline control-flow block statement.	Any	Yes
blank-line-after-terminal-control-block	Missing blank line after terminal control-flow block.	Any	Yes
blank-line-before-branch	Missing blank line before return/raise/break/continue in a large suite.	Any	Yes
blank-line-before-unrelated-block	Illegal cuddle before block header. The preceding setup must directly feed the upcoming block.	Any	Yes
no-suite-leading-trailing-blank-lines	Leading or trailing blank lines in a suite are not allowed.	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	Do not translate exceptions by passing str(exc); use a stable message and chain the cause.	Any	No
no-underscore-class	Class names must not start with an underscore prefix.	Any	No
public-method-order	Define public methods before private helpers in behavior classes.	Any	No

Typing

Rules for type annotations and modern typing syntax.

Enable with:

enable = ["typing"]

Rule	Message	Python	Autofix
no-bare-object-annotations	Use a narrower type than bare object in annotations.	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	Instead of NamedTuple, consider using the @dataclass decorator from dataclasses instead for simplicity, efficiency and consistency.	Any	Yes
no-static-if-condition	Your if condition appears to evaluate to a static value (e.g. or True, and False). Please double check this logic and if it is actually temporary debug code.	Any	No
sorted-attributes	It appears you are using the @sorted-attributes directive and the class variables are unsorted. See the lint autofix suggestion.	Any	Yes
use-callable-ellipsis	Use Callable[…, T] instead of Callable[[…], T].	Any	Yes
use-rattle-ignore-comment	noqa is deprecated. Use rattle: ignore[rule-name] instead.	Any	No
use-types-from-typing	You are using builtins.{builtin_type} as a type annotation but the type system doesn’t recognize it as a valid type. 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	Yes
deprecated-unittest-asserts	{deprecated} is deprecated, use {replacement} instead	Any	Yes
no-inherit-from-object	Inheriting from object is a no-op. ‘class Foo:’ is just fine =)	Any	Yes
no-or-in-except	Avoid using ‘or’ in an except block. For example:’except ValueError or TypeError’ only catches ‘ValueError’. Instead, use parentheses, ‘except (ValueError, TypeError)’	Any	No
no-redundant-arguments-super	Do not use arguments when calling super for the parent class.	Any	Yes
no-redundant-f-string	f-string doesn’t have placeholders, remove redundant f-string.	Any	Yes
no-redundant-lambda	The lambda that is wrapping {function} is redundant. It can unwrapped safely and used purely.	Any	Yes
no-redundant-list-comprehension	Unnecessary list comprehension inside {func}(). Use a generator expression instead.	Any	Yes
no-string-type-annotation	String type hints are no longer necessary in Python, use the type identifier directly.	Any	Yes
replace-union-with-optional	Optional[T] is preferred over Union[T, None] or Union[None, T].	Any	Yes
use-assert-equal	“assertTrue” does not compare its arguments, use “assertEqual” or other appropriate functions.	Any	Yes
use-assert-in	Use assertIn/assertNotIn instead of assertTrue/assertFalse for inclusion check.	Any	Yes
use-assert-is-not-none	“assertTrue” and “assertFalse” are deprecated. Use “assertIsNotNone” and “assertIsNone” instead.	Any	Yes
use-async-sleep-in-async-def	Use asyncio.sleep in async function	Any	No
use-cls-in-classmethod	When using @classmethod, the first argument must be cls.	Any	Yes
use-collections-abc	ABCs must be imported from collections.abc	>= 3.3	Yes
use-comprehension	It’s unnecessary to use {func} around a generator expression, since there are equivalent comprehensions for this type.	Any	Yes
use-eq-for-primitives	Don’t use is or is not to compare primitives, as they compare references. Use == or != instead.	Any	Yes
use-f-string	Do not use printf style formatting or .format(). Use f-string instead to be more readable and efficient.	Any	Yes
use-is-for-singletons	Comparisons to singleton primitives should not be done with == or !=, as they check equality rather than identity. Use is or is not instead.	Any	Yes
use-literal	It’s unnecessary to use a list or tuple within a call to {func} since there is literal syntax for this type	Any	Yes