align-colons
AlignmentPads the space before : so consecutive dict entries, annotated assignments, signature annotations, and docstring entries share one column, with a docstring entry's parenthesized type in a column of its own.
Auto-Fix Rules
An auto-fix rule rewrites source under prose format and reports each rewrite as a Severity::Format diagnostic under prose check. Each rule settles one layout question Prose can answer mechanically (an alignment column, an alphabetical order, a blank-line count, a collection layout, a trailing comma) and emits an Edit list the Pipeline applies between rules. An auto-fix rule never reports a change the binary will not itself write.
align-comments
AlignmentPads the gap before each trailing comment in a run so every # sits at one shared column.
align-comparisons
AlignmentPads the space before each comparison operator in a multi-line and or or chain so the operators share one column.
align-equals
AlignmentPads the space before = so consecutive assignments, annotated parameter defaults, and an exploded call's keyword arguments share one column.
align-imports
AlignmentPads the space before the import keyword across consecutive from imports, or before as across consecutive aliased imports, so the keywords share one column.
align-match-case
AlignmentFolds each single-statement case arm onto one line and pads the space before its : so consecutive arms share one column.
alphabetize-siblings
OrderingSorts sibling entries whose order carries no meaning, covering import names, dict keys, class-body members, keyword arguments, and docstring entries.
band-constants
OrderingMoves module-level constants into a leading band below the imports and a trailing band below the definitions, and sorts each band.
expand-docstrings
DocsExpands a single-line triple-quoted docstring so its opener, its body, and its closer each sit on a line of their own.
frame-docstrings
DocsRewrites a docstring's quotes to the triple-double-quote form and puts a multi-line docstring's opener and closer on their own lines.
group-imports
OrderingMoves each import in a run into its section, __future__ first, then bare, then external from, then local-package.
modernize-annotations
FormattingRewrites Optional[T], Union[X, Y], and the typing generics to the T | None, X | Y, and builtin forms the target runtime supports.
normalize-comment-spacing
FormattingPuts one space after a comment's hash run and at least two spaces between code and a trailing comment.
normalize-comparisons
FormattingRewrites a comparison to state its check directly, using is against None, putting the variable side first, and folding a leading not into its operator.
normalize-literals
FormattingRewrites every string and numeric literal to one spelling of quote character, string prefix, and numeric case.
prefer-fstring
FormattingConverts printf-style % interpolation and str.format() calls to f-strings wherever both forms render the same text.
prune-inert-imports
FormattingRemoves an import that binds a name nothing references or repeats a binding an earlier import already made, and reports the unreferenced one in a package __init__.py instead of removing it.
reflow-calls
LayoutExplodes a call to one keyword argument per line once its argument count passes max-args, its width passes code-line-length, or an argument spans rows, and rejoins a list broken anywhere else onto one row.
reflow-collections
LayoutExpands a list, tuple, dict, or set literal across lines once it overflows code-line-length or a dict passes max-dict-entries, and rejoins a construct broken anywhere but an entry boundary.
reflow-imports
LayoutSplits a from … import … that overflows import-line-length into repeated-prefix statements, breaks a comma-joined import a, b into one statement per module, and merges repeated from statements of one module into one line.
reflow-parentheses
LayoutRemoves a grouping parenthesis pair that changes nothing, and breaks one whose joined form overflows code-line-length into a row per operand.
reflow-signatures
LayoutWrites a function signature either on one line or one parameter per line, expanding it once it overflows code-line-length, passes max-params, or carries a parameter spanning rows.
shed-backslash-continuations
FormattingRemoves a trailing backslash and rejoins its statement, adding parentheses where the joined line would overflow the budget.
shed-redundant-base
FormattingRemoves an explicit object base and the empty parentheses on a class header with no bases.
shed-super-args
FormattingRemoves the class and instance arguments from a super(C, self) call, leaving the bare super() the interpreter resolves on its own.
simplify-comprehensions
FormattingRemoves a collection constructor wrapped around a literal, comprehension, or generator that already builds that collection, and replaces a comprehension that copies its input unchanged with the constructor call.
space-statements
FormattingSets the blank-line count between module-level definitions, class members, import groups, and the __main__ guard to PEP 8's canonical values.
stack-adjacent-strings
LayoutBreaks a run of implicitly concatenated string literals to one literal per line once the joined line overflows code-line-length.
stack-method-chains
LayoutBreaks a method chain to one link per line once it overflows code-line-length or carries more links than max-links, hanging each link beneath the head's dot.
strip-none-return
FormattingRemoves a bare -> None return annotation, since an omitted one already reads as returning nothing.
strip-stranded-padding
AlignmentRemoves padding that lines up with nothing, before the : of a one-member group and just inside a bracket, and settles the gap after a : to one space.
strip-trailing-commas
FormattingRemoves the trailing comma from a collection, signature, call, class base list, or type-parameter list, leaving tuples alone.
wrap-docstrings
DocsWraps a docstring's description prose to docstring-line-length and its Title-case-headed sections to the budget docstring-structured-policy selects.
The Pipeline Order reference lists the fixed order these rules run in, the Configuration reference lists the per-rule facets, and the Lint landing covers the rules that report a diagnostic without rewriting.