Black classes¶
Contents are subject to change.
BracketTracker
¶
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class
black.brackets.
BracketTracker
(depth: int = 0, bracket_match: Dict[Tuple[int, int], blib2to3.pytree.Leaf] = <factory>, delimiters: Dict[int, int] = <factory>, previous: Optional[blib2to3.pytree.Leaf] = None, _for_loop_depths: List[int] = <factory>, _lambda_argument_depths: List[int] = <factory>, invisible: List[blib2to3.pytree.Leaf] = <factory>)¶ Keeps track of brackets on a line.
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mark
(leaf: blib2to3.pytree.Leaf) → None¶ Mark leaf with bracket-related metadata. Keep track of delimiters.
All leaves receive an int bracket_depth field that stores how deep within brackets a given leaf is. 0 means there are no enclosing brackets that started on this line.
If a leaf is itself a closing bracket, it receives an opening_bracket field that it forms a pair with. This is a one-directional link to avoid reference cycles.
If a leaf is a delimiter (a token on which Black can split the line if needed) and it’s on depth 0, its id() is stored in the tracker’s delimiters field.
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max_delimiter_priority
(exclude: Iterable[int] = ()) → int¶ Return the highest priority of a delimiter found on the line.
Values are consistent with what is_split_*_delimiter() return. Raises ValueError on no delimiters.
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delimiter_count_with_priority
(priority: int = 0) → int¶ Return the number of delimiters with the given priority.
If no priority is passed, defaults to max priority on the line.
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maybe_increment_for_loop_variable
(leaf: blib2to3.pytree.Leaf) → bool¶ In a for loop, or comprehension, the variables are often unpacks.
To avoid splitting on the comma in this situation, increase the depth of tokens between for and in.
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maybe_decrement_after_for_loop_variable
(leaf: blib2to3.pytree.Leaf) → bool¶ See maybe_increment_for_loop_variable above for explanation.
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maybe_increment_lambda_arguments
(leaf: blib2to3.pytree.Leaf) → bool¶ In a lambda expression, there might be more than one argument.
To avoid splitting on the comma in this situation, increase the depth of tokens between lambda and :.
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maybe_decrement_after_lambda_arguments
(leaf: blib2to3.pytree.Leaf) → bool¶ See maybe_increment_lambda_arguments above for explanation.
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get_open_lsqb
() → Optional[blib2to3.pytree.Leaf]¶ Return the most recent opening square bracket (if any).
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EmptyLineTracker
¶
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class
black.
EmptyLineTracker
(is_pyi: bool = False, previous_line: Optional[black.lines.Line] = None, previous_after: int = 0, previous_defs: List[int] = <factory>)¶ Provides a stateful method that returns the number of potential extra empty lines needed before and after the currently processed line.
Note: this tracker works on lines that haven’t been split yet. It assumes the prefix of the first leaf consists of optional newlines. Those newlines are consumed by maybe_empty_lines() and included in the computation.
Line
¶
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class
black.
Line
(mode: black.mode.Mode, depth: int = 0, leaves: List[blib2to3.pytree.Leaf] = <factory>, comments: Dict[int, List[blib2to3.pytree.Leaf]] = <factory>, bracket_tracker: black.brackets.BracketTracker = <factory>, inside_brackets: bool = False, should_split_rhs: bool = False, magic_trailing_comma: Optional[blib2to3.pytree.Leaf] = None)¶ Holds leaves and comments. Can be printed with str(line).
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append
(leaf: blib2to3.pytree.Leaf, preformatted: bool = False) → None¶ Add a new leaf to the end of the line.
Unless preformatted is True, the leaf will receive a new consistent whitespace prefix and metadata applied by
BracketTracker
. Trailing commas are maybe removed, unpacked for loop variables are demoted from being delimiters.Inline comments are put aside.
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append_safe
(leaf: blib2to3.pytree.Leaf, preformatted: bool = False) → None¶ Like
append()
but disallow invalid standalone comment structure.Raises ValueError when any leaf is appended after a standalone comment or when a standalone comment is not the first leaf on the line.
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property
is_comment
¶ Is this line a standalone comment?
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property
is_decorator
¶ Is this line a decorator?
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property
is_import
¶ Is this an import line?
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property
is_class
¶ Is this line a class definition?
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property
is_stub_class
¶ Is this line a class definition with a body consisting only of “…”?
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property
is_def
¶ Is this a function definition? (Also returns True for async defs.)
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property
is_class_paren_empty
¶ Is this a class with no base classes but using parentheses?
Those are unnecessary and should be removed.
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property
is_triple_quoted_string
¶ Is the line a triple quoted string?
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contains_standalone_comments
(depth_limit: int = 9223372036854775807) → bool¶ If so, needs to be split before emitting.
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has_magic_trailing_comma
(closing: blib2to3.pytree.Leaf, ensure_removable: bool = False) → bool¶ Return True if we have a magic trailing comma, that is when: - there’s a trailing comma here - it’s not a one-tuple Additionally, if ensure_removable: - it’s not from square bracket indexing
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append_comment
(comment: blib2to3.pytree.Leaf) → bool¶ Add an inline or standalone comment to the line.
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comments_after
(leaf: blib2to3.pytree.Leaf) → List[blib2to3.pytree.Leaf]¶ Generate comments that should appear directly after leaf.
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is_complex_subscript
(leaf: blib2to3.pytree.Leaf) → bool¶ Return True iff leaf is part of a slice with non-trivial exprs.
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LineGenerator
¶
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class
black.
LineGenerator
(mode: black.mode.Mode, remove_u_prefix: bool = False)¶ Bases:
black.nodes.Visitor
[black.lines.Line
]Generates reformatted Line objects. Empty lines are not emitted.
Note: destroys the tree it’s visiting by mutating prefixes of its leaves in ways that will no longer stringify to valid Python code on the tree.
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line
(indent: int = 0) → Iterator[black.lines.Line]¶ Generate a line.
If the line is empty, only emit if it makes sense. If the line is too long, split it first and then generate.
If any lines were generated, set up a new current_line.
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visit_default
(node: Union[blib2to3.pytree.Leaf, blib2to3.pytree.Node]) → Iterator[black.lines.Line]¶ Default visit_*() implementation. Recurses to children of node.
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visit_INDENT
(node: blib2to3.pytree.Leaf) → Iterator[black.lines.Line]¶ Increase indentation level, maybe yield a line.
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visit_DEDENT
(node: blib2to3.pytree.Leaf) → Iterator[black.lines.Line]¶ Decrease indentation level, maybe yield a line.
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visit_stmt
(node: blib2to3.pytree.Node, keywords: Set[str], parens: Set[str]) → Iterator[black.lines.Line]¶ Visit a statement.
This implementation is shared for if, while, for, try, except, def, with, class, assert and assignments.
The relevant Python language keywords for a given statement will be NAME leaves within it. This methods puts those on a separate line.
parens holds a set of string leaf values immediately after which invisible parens should be put.
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visit_suite
(node: blib2to3.pytree.Node) → Iterator[black.lines.Line]¶ Visit a suite.
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visit_simple_stmt
(node: blib2to3.pytree.Node) → Iterator[black.lines.Line]¶ Visit a statement without nested statements.
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visit_async_stmt
(node: blib2to3.pytree.Node) → Iterator[black.lines.Line]¶ Visit async def, async for, async with.
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visit_decorators
(node: blib2to3.pytree.Node) → Iterator[black.lines.Line]¶ Visit decorators.
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visit_SEMI
(leaf: blib2to3.pytree.Leaf) → Iterator[black.lines.Line]¶ Remove a semicolon and put the other statement on a separate line.
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visit_ENDMARKER
(leaf: blib2to3.pytree.Leaf) → Iterator[black.lines.Line]¶ End of file. Process outstanding comments and end with a newline.
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visit_factor
(node: blib2to3.pytree.Node) → Iterator[black.lines.Line]¶ Force parentheses between a unary op and a binary power:
-2 ** 8 -> -(2 ** 8)
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ProtoComment
¶
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class
black.comments.
ProtoComment
(type: int, value: str, newlines: int, consumed: int)¶ Describes a piece of syntax that is a comment.
It’s not a
blib2to3.pytree.Leaf
so that:it can be cached (Leaf objects should not be reused more than once as they store their lineno, column, prefix, and parent information);
newlines and consumed fields are kept separate from the value. This simplifies handling of special marker comments like
# fmt: off/on
.
Report
¶
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class
black.
Report
(check: bool = False, diff: bool = False, quiet: bool = False, verbose: bool = False, change_count: int = 0, same_count: int = 0, failure_count: int = 0)¶ Provides a reformatting counter. Can be rendered with str(report).
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done
(src: pathlib.Path, changed: black.report.Changed) → None¶ Increment the counter for successful reformatting. Write out a message.
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failed
(src: pathlib.Path, message: str) → None¶ Increment the counter for failed reformatting. Write out a message.
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property
return_code
¶ Return the exit code that the app should use.
This considers the current state of changed files and failures: - if there were any failures, return 123; - if any files were changed and –check is being used, return 1; - otherwise return 0.
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Visitor
¶
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class
black.nodes.
Visitor
(*args, **kwds)¶ Bases:
Generic
[black.nodes.T
]Basic lib2to3 visitor that yields things of type T on visit().
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visit
(node: Union[blib2to3.pytree.Leaf, blib2to3.pytree.Node]) → Iterator[T]¶ Main method to visit node and its children.
It tries to find a visit_*() method for the given node.type, like visit_simple_stmt for Node objects or visit_INDENT for Leaf objects. If no dedicated visit_*() method is found, chooses visit_default() instead.
Then yields objects of type T from the selected visitor.
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visit_default
(node: Union[blib2to3.pytree.Leaf, blib2to3.pytree.Node]) → Iterator[T]¶ Default visit_*() implementation. Recurses to children of node.
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