Black classes¶
Contents are subject to change.
BracketTracker
¶
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class
black.
BracketTracker
(depth=0, bracket_match=NOTHING, delimiters=NOTHING, previous=None)¶ 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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any_open_brackets
() → bool¶ Return True if there is an yet unmatched open bracket on the line.
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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_delimiter() returns.
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EmptyLineTracker
¶
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class
black.
EmptyLineTracker
(previous_line=None, previous_after=0, previous_defs=NOTHING)¶ 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.
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maybe_empty_lines
(current_line: black.Line) → Tuple[int, int]¶ Return the number of extra empty lines before and after the current_line.
This is for separating def, async def and class with extra empty lines (two on module-level), as well as providing an extra empty line after flow control keywords to make them more prominent.
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Line
¶
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class
black.
Line
(depth=0, leaves=NOTHING, comments=NOTHING, bracket_tracker=NOTHING, inside_brackets=False, has_for=False, for_loop_variable=False)¶ 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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is_comment
¶ Is this line a standalone comment?
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is_decorator
¶ Is this line a decorator?
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is_import
¶ Is this an import line?
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is_class
¶ Is this line a class definition?
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is_def
¶ Is this a function definition? (Also returns True for async defs.)
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is_flow_control
¶ Is this line a flow control statement?
Those are return, raise, break, and continue.
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is_yield
¶ Is this line a yield statement?
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contains_standalone_comments
¶ If so, needs to be split before emitting.
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maybe_remove_trailing_comma
(closing: blib2to3.pytree.Leaf) → bool¶ Remove trailing comma if there is one and it’s safe.
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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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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) → Iterator[blib2to3.pytree.Leaf]¶ Generate comments that should appear directly after leaf.
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remove_trailing_comma
() → None¶ Remove the trailing comma and moves the comments attached to it.
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__str__
() → str¶ Render the line.
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__bool__
() → bool¶ Return True if the line has leaves or comments.
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LineGenerator
¶
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class
black.
LineGenerator
(current_line=NOTHING)¶ Bases:
black.Visitor
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, type: Type[black.Line] = <class 'black.Line'>) → Iterator[black.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
(node: Union[blib2to3.pytree.Leaf, blib2to3.pytree.Node]) → Iterator[black.Line]¶ Main method to visit node and its children.
Yields
Line
objects.
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visit_default
(node: Union[blib2to3.pytree.Leaf, blib2to3.pytree.Node]) → Iterator[black.Line]¶ Default visit_*() implementation. Recurses to children of node.
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visit_INDENT
(node: blib2to3.pytree.Node) → Iterator[black.Line]¶ Increase indentation level, maybe yield a line.
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visit_DEDENT
(node: blib2to3.pytree.Node) → Iterator[black.Line]¶ Decrease indentation level, maybe yield a line.
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visit_stmt
(node: blib2to3.pytree.Node, keywords: Set[str]) → Iterator[black.Line]¶ Visit a statement.
This implementation is shared for if, while, for, try, except, def, with, and class.
The relevant Python language keywords for a given statement will be NAME leaves within it. This methods puts those on a separate line.
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visit_simple_stmt
(node: blib2to3.pytree.Node) → Iterator[black.Line]¶ Visit a statement without nested statements.
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visit_async_stmt
(node: blib2to3.pytree.Node) → Iterator[black.Line]¶ Visit async def, async for, async with.
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visit_decorators
(node: blib2to3.pytree.Node) → Iterator[black.Line]¶ Visit decorators.
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visit_SEMI
(leaf: blib2to3.pytree.Leaf) → Iterator[black.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.Line]¶ End of file. Process outstanding comments and end with a newline.
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visit_unformatted
(node: Union[blib2to3.pytree.Leaf, blib2to3.pytree.Node]) → Iterator[black.Line]¶ Used when file contained a # fmt: off.
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Report
¶
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class
black.
Report
(check=False, change_count=0, same_count=0, failure_count=0)¶ Provides a reformatting counter. Can be rendered with str(report).
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done
(src: pathlib.Path, changed: bool) → 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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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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__str__
() → str¶ Render a color report of the current state.
Use click.unstyle to remove colors.
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UnformattedLines
¶
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class
black.
UnformattedLines
(depth=0, leaves=NOTHING, comments=NOTHING, bracket_tracker=NOTHING, inside_brackets=False, has_for=False, for_loop_variable=False)¶ Bases:
black.Line
Just like
Line
but stores lines which aren’t reformatted.-
append
(leaf: blib2to3.pytree.Leaf, preformatted: bool = True) → None¶ Just add a new leaf to the end of the lines.
The preformatted argument is ignored.
Keeps track of indentation depth, which is useful when the user says # fmt: on. Otherwise, doesn’t do anything with the leaf.
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__str__
() → str¶ Render unformatted lines from leaves which were added with append().
depth is not used for indentation in this case.
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append_comment
(comment: blib2to3.pytree.Leaf) → bool¶ Not implemented in this class. Raises NotImplementedError.
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maybe_remove_trailing_comma
(closing: blib2to3.pytree.Leaf) → bool¶ Does nothing and returns False.
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maybe_increment_for_loop_variable
(leaf: blib2to3.pytree.Leaf) → bool¶ Does nothing and returns False.
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Visitor
¶
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class
black.
Visitor
¶ Bases:
typing.Generic
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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