The Uncompromising Code Formatter

“Any color you like.”

Black is the uncompromising Python code formatter. By using it, you agree to cede control over minutiae of hand-formatting. In return, Black gives you speed, determinism, and freedom from pycodestyle nagging about formatting. You will save time and mental energy for more important matters.

Blackened code looks the same regardless of the project you're reading. Formatting becomes transparent after a while and you can focus on the content instead.

Black makes code review faster by producing the smallest diffs possible.

Try it out now using the Black Playground. Watch the PyCon 2019 talk to learn more.

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Read the documentation on ReadTheDocs!

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Installation and usage

Installation

Black can be installed by running pip install black. It requires Python 3.9+ to run. If you want to format Jupyter Notebooks, install with pip install "black[jupyter]".

If you can't wait for the latest hotness and want to install from GitHub, use:

pip install git+https://github.com/psf/black

Usage

To get started right away with sensible defaults:

black {source_file_or_directory}

You can run Black as a package if running it as a script doesn't work:

python -m black {source_file_or_directory}

Further information can be found in our docs:

• Usage and Configuration

Black is already successfully used by many projects, small and big. Black has a comprehensive test suite, with efficient parallel tests, and our own auto formatting and parallel Continuous Integration runner. Now that we have become stable, you should not expect large formatting changes in the future. Stylistic changes will mostly be responses to bug reports and support for new Python syntax. For more information please refer to The Black Code Style.

Also, as a safety measure which slows down processing, Black will check that the reformatted code still produces a valid AST that is effectively equivalent to the original (see the Pragmatism section for details). If you're feeling confident, use --fast.

The Black code style

Black is a PEP 8 compliant opinionated formatter. Black reformats entire files in place. Style configuration options are deliberately limited and rarely added. It doesn't take previous formatting into account (see Pragmatism for exceptions).

Our documentation covers the current Black code style, but planned changes to it are also documented. They're both worth taking a look at:

• The Black Code Style: Current style
• The Black Code Style: Future style

Changes to the Black code style are bound by the Stability Policy:

• The Black Code Style: Stability Policy

Please refer to this document before submitting an issue. What seems like a bug might be intended behaviour.

Pragmatism

Early versions of Black used to be absolutist in some respects. They took after its initial author. This was fine at the time as it made the implementation simpler and there were not many users anyway. Not many edge cases were reported. As a mature tool, Black does make some exceptions to rules it otherwise holds.

• The Black code style: Pragmatism

Please refer to this document before submitting an issue just like with the document above. What seems like a bug might be intended behaviour.

Configuration

Black is able to read project-specific default values for its command line options from a pyproject.toml file. This is especially useful for specifying custom --include and --exclude/--force-exclude/--extend-exclude patterns for your project.

You can find more details in our documentation:

• The basics: Configuration via a file

And if you're looking for more general configuration documentation:

• Usage and Configuration

Pro-tip: If you're asking yourself "Do I need to configure anything?" the answer is "No". Black is all about sensible defaults. Applying those defaults will have your code in compliance with many other Black formatted projects.

Used by

The following notable open-source projects trust Black with enforcing a consistent code style: pytest, tox, Pyramid, Django, Django Channels, Hypothesis, attrs, SQLAlchemy, Poetry, PyPA applications (Warehouse, Bandersnatch, Pipenv, virtualenv), pandas, Pillow, Twisted, LocalStack, every Datadog Agent Integration, Home Assistant, Zulip, Kedro, OpenOA, FLORIS, ORBIT, WOMBAT, and many more.

The following organizations use Black: Dropbox, KeepTruckin, Lyft, Mozilla, Quora, Duolingo, QuantumBlack, Tesla, Archer Aviation.

Are we missing anyone? Let us know.

Testimonials

Mike Bayer, author of SQLAlchemy:

I can't think of any single tool in my entire programming career that has given me a bigger productivity increase by its introduction. I can now do refactorings in about 1% of the keystrokes that it would have taken me previously when we had no way for code to format itself.

Dusty Phillips, writer:

Black is opinionated so you don't have to be.

Hynek Schlawack, creator of attrs, core developer of Twisted and CPython:

An auto-formatter that doesn't suck is all I want for Xmas!

Carl Meyer, Django core developer:

At least the name is good.

Kenneth Reitz, creator of requests and pipenv:

This vastly improves the formatting of our code. Thanks a ton!

Show your style

Use the badge in your project's README.md:

[![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)

Using the badge in README.rst:

.. image:: https://img.shields.io/badge/code%20style-black-000000.svg
    :target: https://github.com/psf/black

Looks like this:

License

MIT

Contributing

Welcome! Happy to see you willing to make the project better. You can get started by reading this:

• Contributing: The basics

You can also take a look at the rest of the contributing docs or talk with the developers:

• Contributing documentation
• Chat on Discord

Change log

The log has become rather long. It moved to its own file.

See CHANGES.

Authors

The author list is quite long nowadays, so it lives in its own file.

See AUTHORS.md

Code of Conduct

Everyone participating in the Black project, and in particular in the issue tracker, pull requests, and social media activity, is expected to treat other people with respect and more generally to follow the guidelines articulated in the Python Community Code of Conduct.

At the same time, humor is encouraged. In fact, basic familiarity with Monty Python's Flying Circus is expected. We are not savages.

And if you really need to slap somebody, do it with a fish while dancing.

Change Log

25.9.0

Highlights

• Remove support for pre-python 3.7 await/async as soft keywords/variable names (#4676)

Stable style

• Fix crash while formatting a long del statement containing tuples (#4628)
• Fix crash while formatting expressions using the walrus operator in complex with statements (#4630)
• Handle # fmt: skip followed by a comment at the end of file (#4635)
• Fix crash when a tuple appears in the as clause of a with statement (#4634)
• Fix crash when tuple is used as a context manager inside a with statement (#4646)
• Fix crash when formatting a \ followed by a \r followed by a comment (#4663)
• Fix crash on a \\r\n (#4673)
• Fix crash on await ... (where ... is a literal Ellipsis) (#4676)
• Fix crash on parenthesized expression inside a type parameter bound (#4684)
• Fix crash when using line ranges excluding indented single line decorated items (#4670)

Preview style

• Fix a bug where one-liner functions/conditionals marked with # fmt: skip would still be formatted (#4552)
• Improve multiline_string_handling with ternaries and dictionaries (#4657)
• Fix a bug where string_processing would not split f-strings directly after expressions (#4680)
• Wrap the in clause of comprehensions across lines if necessary (#4699)
• Remove parentheses around multiple exception types in except and except* without as. (#4720)
• Add \r style newlines to the potential newlines to normalize file newlines both from and to (#4710)

Parser

• Rewrite tokenizer to improve performance and compliance (#4536)
• Fix bug where certain unusual expressions (e.g., lambdas) were not accepted in type parameter bounds and defaults. (#4602)

Performance

• Avoid using an extra process when running with only one worker (#4734)

Integrations

• Fix the version check in the vim file to reject Python 3.8 (#4567)
• Enhance GitHub Action psf/black to read Black version from an additional section in pyproject.toml: [project.dependency-groups] (#4606)
• Build gallery docker image with python3-slim and reduce image size (#4686)

Documentation

• Add FAQ entry for windows emoji not displaying (#4714)

25.1.0

Highlights

This release introduces the new 2025 stable style (#4558), stabilizing the following changes:

• Normalize casing of Unicode escape characters in strings to lowercase (#2916)
• Fix inconsistencies in whether certain strings are detected as docstrings (#4095)
• Consistently add trailing commas to typed function parameters (#4164)
• Remove redundant parentheses in if guards for case blocks (#4214)
• Add parentheses to if clauses in case blocks when the line is too long (#4269)
• Whitespace before # fmt: skip comments is no longer normalized (#4146)
• Fix line length computation for certain expressions that involve the power operator (#4154)
• Check if there is a newline before the terminating quotes of a docstring (#4185)
• Fix type annotation spacing between * and more complex type variable tuple (#4440)

The following changes were not in any previous release:

• Remove parentheses around sole list items (#4312)
• Generic function definitions are now formatted more elegantly: parameters are split over multiple lines first instead of type parameter definitions (#4553)

Stable style

• Fix formatting cells in IPython notebooks with magic methods and starting or trailing empty lines (#4484)
• Fix crash when formatting with statements containing tuple generators/unpacking (#4538)

Preview style

• Fix/remove string merging changing f-string quotes on f-strings with internal quotes (#4498)
• Collapse multiple empty lines after an import into one (#4489)
• Prevent string_processing and wrap_long_dict_values_in_parens from removing parentheses around long dictionary values (#4377)
• Move wrap_long_dict_values_in_parens from the unstable to preview style (#4561)

Packaging

• Store license identifier inside the License-Expression metadata field, see PEP 639. (#4479)

Performance

• Speed up the is_fstring_start function in Black's tokenizer (#4541)

Integrations

• If using stdin with --stdin-filename set to a force excluded path, stdin won't be formatted. (#4539)

24.10.0

Highlights

• Black is now officially tested with Python 3.13 and provides Python 3.13 mypyc-compiled wheels. (#4436) (#4449)
• Black will issue an error when used with Python 3.12.5, due to an upstream memory safety issue in Python 3.12.5 that can cause Black's AST safety checks to fail. Please use Python 3.12.6 or Python 3.12.4 instead. (#4447)
• Black no longer supports running with Python 3.8 (#4452)

Stable style

• Fix crashes involving comments in parenthesised return types or X | Y style unions. (#4453)
• Fix skipping Jupyter cells with unknown %% magic (#4462)

Preview style

• Fix type annotation spacing between * and more complex type variable tuple (i.e. def fn(*args: *tuple[*Ts, T]) -> None: pass) (#4440)

Caching

• Fix bug where the cache was shared between runs with and without --unstable (#4466)

Packaging

• Upgrade version of mypyc used to 1.12 beta (#4450) (#4449)
• blackd now requires a newer version of aiohttp. (#4451)

Output

• Added Python target version information on parse error (#4378)
• Add information about Black version to internal error messages (#4457)

24.8.0

Stable style

• Fix crash when # fmt: off is used before a closing parenthesis or bracket. (#4363)

Packaging

• Packaging metadata updated: docs are explictly linked, the issue tracker is now also linked. This improves the PyPI listing for Black. (#4345)

Parser

• Fix regression where Black failed to parse a multiline f-string containing another multiline string (#4339)
• Fix regression where Black failed to parse an escaped single quote inside an f-string (#4401)
• Fix bug with Black incorrectly parsing empty lines with a backslash (#4343)
• Fix bugs with Black's tokenizer not handling \{ inside f-strings very well (#4422)
• Fix incorrect line numbers in the tokenizer for certain tokens within f-strings (#4423)

Performance

• Improve performance when a large directory is listed in .gitignore (#4415)

Blackd

• Fix blackd (and all extras installs) for docker container (#4357)

24.4.2

This is a bugfix release to fix two regressions in the new f-string parser introduced in 24.4.1.

Parser

• Fix regression where certain complex f-strings failed to parse (#4332)

Performance

• Fix bad performance on certain complex string literals (#4331)

24.4.1

Highlights

• Add support for the new Python 3.12 f-string syntax introduced by PEP 701 (#3822)

Stable style

• Fix crash involving indented dummy functions containing newlines (#4318)

Parser

• Add support for type parameter defaults, a new syntactic feature added to Python 3.13 by PEP 696 (#4327)

Integrations

• Github Action now works even when git archive is skipped (#4313)

24.4.0

Stable style

• Fix unwanted crashes caused by AST equivalency check (#4290)

Preview style

• if guards in case blocks are now wrapped in parentheses when the line is too long. (#4269)
• Stop moving multiline strings to a new line unless inside brackets (#4289)

Integrations

• Add a new option use_pyproject to the GitHub Action psf/black. This will read the Black version from pyproject.toml. (#4294)

24.3.0

Highlights

This release is a milestone: it fixes Black's first CVE security vulnerability. If you run Black on untrusted input, or if you habitually put thousands of leading tab characters in your docstrings, you are strongly encouraged to upgrade immediately to fix CVE-2024-21503.

This release also fixes a bug in Black's AST safety check that allowed Black to make incorrect changes to certain f-strings that are valid in Python 3.12 and higher.

Stable style

• Don't move comments along with delimiters, which could cause crashes (#4248)
• Strengthen AST safety check to catch more unsafe changes to strings. Previous versions of Black would incorrectly format the contents of certain unusual f-strings containing nested strings with the same quote type. Now, Black will crash on such strings until support for the new f-string syntax is implemented. (#4270)
• Fix a bug where line-ranges exceeding the last code line would not work as expected (#4273)

Performance

• Fix catastrophic performance on docstrings that contain large numbers of leading tab characters. This fixes CVE-2024-21503. (#4278)

Documentation

• Note what happens when --check is used with --quiet (#4236)

24.2.0

Stable style

• Fixed a bug where comments where mistakenly removed along with redundant parentheses (#4218)

Preview style

• Move the hug_parens_with_braces_and_square_brackets feature to the unstable style due to an outstanding crash and proposed formatting tweaks (#4198)
• Fixed a bug where base expressions caused inconsistent formatting of ** in tenary expression (#4154)
• Checking for newline before adding one on docstring that is almost at the line limit (#4185)
• Remove redundant parentheses in case statement if guards (#4214).

Configuration

• Fix issue where Black would ignore input files in the presence of symlinks (#4222)
• Black now ignores pyproject.toml that is missing a tool.black section when discovering project root and configuration. Since Black continues to use version control as an indicator of project root, this is expected to primarily change behavior for users in a monorepo setup (desirably). If you wish to preserve previous behavior, simply add an empty [tool.black] to the previously discovered pyproject.toml (#4204)

Output

• Black will swallow any SyntaxWarnings or DeprecationWarnings produced by the ast module when performing equivalence checks (#4189)

Integrations

• Add a JSONSchema and provide a validate-pyproject entry-point (#4181)

24.1.1

Bugfix release to fix a bug that made Black unusable on certain file systems with strict limits on path length.

Preview style

• Consistently add trailing comma on typed parameters (#4164)

Configuration

• Shorten the length of the name of the cache file to fix crashes on file systems that do not support long paths (#4176)

24.1.0

Highlights

This release introduces the new 2024 stable style (#4106), stabilizing the following changes:

• Add parentheses around if-else expressions (#2278)
• Dummy class and function implementations consisting only of ... are formatted more compactly (#3796)
• If an assignment statement is too long, we now prefer splitting on the right-hand side (#3368)
• Hex codes in Unicode escape sequences are now standardized to lowercase (#2916)
• Allow empty first lines at the beginning of most blocks (#3967, #4061)
• Add parentheses around long type annotations (#3899)
• Enforce newline after module docstrings (#3932, #4028)
• Fix incorrect magic trailing comma handling in return types (#3916)
• Remove blank lines before class docstrings (#3692)
• Wrap multiple context managers in parentheses if combined in a single with statement (#3489)
• Fix bug in line length calculations for power operations (#3942)
• Add trailing commas to collection literals even if there's a comment after the last entry (#3393)
• When using --skip-magic-trailing-comma or -C, trailing commas are stripped from subscript expressions with more than 1 element (#3209)
• Add extra blank lines in stubs in a few cases (#3564, #3862)
• Accept raw strings as docstrings (#3947)
• Split long lines in case blocks (#4024)
• Stop removing spaces from walrus operators within subscripts (#3823)
• Fix incorrect formatting of certain async statements (#3609)
• Allow combining # fmt: skip with other comments (#3959)

There are already a few improvements in the --preview style, which are slated for the 2025 stable style. Try them out and share your feedback. In the past, the preview style has included some features that we were not able to stabilize. This year, we're adding a separate --unstable style for features with known problems. Now, the --preview style only includes features that we actually expect to make it into next year's stable style.

Stable style

Several bug fixes were made in features that are moved to the stable style in this release:

• Fix comment handling when parenthesising conditional expressions (#4134)
• Fix bug where spaces were not added around parenthesized walruses in subscripts, unlike other binary operators (#4109)
• Remove empty lines before docstrings in async functions (#4132)
• Address a missing case in the change to allow empty lines at the beginning of all blocks, except immediately before a docstring (#4130)
• For stubs, fix logic to enforce empty line after nested classes with bodies (#4141)

Preview style

• Add --unstable style, covering preview features that have known problems that would block them from going into the stable style. Also add the --enable-unstable-feature flag; for example, use --enable-unstable-feature hug_parens_with_braces_and_square_brackets to apply this preview feature throughout 2024, even if a later Black release downgrades the feature to unstable (#4096)
• Format module docstrings the same as class and function docstrings (#4095)
• Fix crash when using a walrus in a dictionary (#4155)
• Fix unnecessary parentheses when wrapping long dicts (#4135)
• Stop normalizing spaces before # fmt: skip comments (#4146)

Configuration

• Print warning when configuration in pyproject.toml contains an invalid key (#4165)
• Fix symlink handling, properly ignoring symlinks that point outside of root (#4161)
• Fix cache mtime logic that resulted in false positive cache hits (#4128)
• Remove the long-deprecated --experimental-string-processing flag. This feature can currently be enabled with --preview --enable-unstable-feature string_processing. (#4096)

Integrations

• Revert the change to run Black's pre-commit integration only on specific git hooks (#3940) for better compatibility with older versions of pre-commit (#4137)

23.12.1

Packaging

• Fixed a bug that included dependencies from the d extra by default (#4108)

23.12.0

Highlights

It's almost 2024, which means it's time for a new edition of Black's stable style! Together with this release, we'll put out an alpha release 24.1a1 showcasing the draft 2024 stable style, which we'll finalize in the January release. Please try it out and share your feedback.

This release (23.12.0) will still produce the 2023 style. Most but not all of the changes in --preview mode will be in the 2024 stable style.

Stable style

• Fix bug where # fmt: off automatically dedents when used with the --line-ranges option, even when it is not within the specified line range. (#4084)
• Fix feature detection for parenthesized context managers (#4104)

Preview style

• Prefer more equal signs before a break when splitting chained assignments (#4010)
• Standalone form feed characters at the module level are no longer removed (#4021)
• Additional cases of immediately nested tuples, lists, and dictionaries are now indented less (#4012)
• Allow empty lines at the beginning of all blocks, except immediately before a docstring (#4060)
• Fix crash in preview mode when using a short --line-length (#4086)
• Keep suites consisting of only an ellipsis on their own lines if they are not functions or class definitions (#4066) (#4103)

Configuration

• --line-ranges now skips Black's internal stability check in --safe mode. This avoids a crash on rare inputs that have many unformatted same-content lines. (#4034)

Packaging

• Upgrade to mypy 1.7.1 (#4049) (#4069)
• Faster compiled wheels are now available for CPython 3.12 (#4070)

Integrations

• Enable 3.12 CI (#4035)
• Build docker images in parallel (#4054)
• Build docker images with 3.12 (#4055)

23.11.0

Highlights

• Support formatting ranges of lines with the new --line-ranges command-line option (#4020)

Stable style

• Fix crash on formatting bytes strings that look like docstrings (#4003)
• Fix crash when whitespace followed a backslash before newline in a docstring (#4008)
• Fix standalone comments inside complex blocks crashing Black (#4016)
• Fix crash on formatting code like await (a ** b) (#3994)
• No longer treat leading f-strings as docstrings. This matches Python's behaviour and fixes a crash (#4019)

Preview style

• Multiline dicts and lists that are the sole argument to a function are now indented less (#3964)
• Multiline unpacked dicts and lists as the sole argument to a function are now also indented less (#3992)
• In f-string debug expressions, quote types that are visible in the final string are now preserved (#4005)
• Fix a bug where long case blocks were not split into multiple lines. Also enable general trailing comma rules on case blocks (#4024)
• Keep requiring two empty lines between module-level docstring and first function or class definition (#4028)
• Add support for single-line format skip with other comments on the same line (#3959)

Configuration

• Consistently apply force exclusion logic before resolving symlinks (#4015)
• Fix a bug in the matching of absolute path names in --include (#3976)

Performance

• Fix mypyc builds on arm64 on macOS (#4017)

Integrations

• Black's pre-commit integration will now run only on git hooks appropriate for a code formatter (#3940)

23.10.1

Highlights

• Maintenance release to get a fix out for GitHub Action edge case (#3957)

Preview style

• Fix merging implicit multiline strings that have inline comments (#3956)
• Allow empty first line after block open before a comment or compound statement (#3967)

Packaging

• Change Dockerfile to hatch + compile black (#3965)

Integrations

• The summary output for GitHub workflows is now suppressible using the summary parameter. (#3958)
• Fix the action failing when Black check doesn't pass (#3957)

Documentation

• It is known Windows documentation CI is broken https://github.com/psf/black/issues/3968

23.10.0

Stable style

• Fix comments getting removed from inside parenthesized strings (#3909)

Preview style

• Fix long lines with power operators getting split before the line length (#3942)
• Long type hints are now wrapped in parentheses and properly indented when split across multiple lines (#3899)
• Magic trailing commas are now respected in return types. (#3916)
• Require one empty line after module-level docstrings. (#3932)
• Treat raw triple-quoted strings as docstrings (#3947)

Configuration

• Fix cache versioning logic when BLACK_CACHE_DIR is set (#3937)

Parser

• Fix bug where attributes named type were not accepted inside match statements (#3950)
• Add support for PEP 695 type aliases containing lambdas and other unusual expressions (#3949)

Output

• Black no longer attempts to provide special errors for attempting to format Python 2 code (#3933)
• Black will more consistently print stacktraces on internal errors in verbose mode (#3938)

Integrations

• The action output displayed in the job summary is now wrapped in Markdown (#3914)

23.9.1

Due to various issues, the previous release (23.9.0) did not include compiled mypyc wheels, which make Black significantly faster. These issues have now been fixed, and this release should come with compiled wheels once again.

There will be no wheels for Python 3.12 due to a bug in mypyc. We will provide 3.12 wheels in a future release as soon as the mypyc bug is fixed.

Packaging

• Upgrade to mypy 1.5.1 (#3864)

Performance

• Store raw tuples instead of NamedTuples in Black's cache, improving performance and decreasing the size of the cache (#3877)

23.9.0

Preview style

• More concise formatting for dummy implementations (#3796)
• In stub files, add a blank line between a statement with a body (e.g an if sys.version_info > (3, x):) and a function definition on the same level (#3862)
• Fix a bug whereby spaces were removed from walrus operators within subscript(#3823)

Configuration

• Black now applies exclusion and ignore logic before resolving symlinks (#3846)

Performance

• Avoid importing IPython if notebook cells do not contain magics (#3782)
• Improve caching by comparing file hashes as fallback for mtime and size (#3821)

Blackd

• Fix an issue in blackd with single character input (#3558)

Integrations

• Black now has an official pre-commit mirror. Swapping https://github.com/psf/black to https://github.com/psf/black-pre-commit-mirror in your .pre-commit-config.yaml will make Black about 2x faster (#3828)
• The .black.env folder specified by ENV_PATH will now be removed on the completion of the GitHub Action (#3759)

23.7.0

Highlights

• Runtime support for Python 3.7 has been removed. Formatting 3.7 code will still be supported until further notice (#3765)

Stable style

• Fix a bug where an illegal trailing comma was added to return type annotations using PEP 604 unions (#3735)
• Fix several bugs and crashes where comments in stub files were removed or mishandled under some circumstances (#3745)
• Fix a crash with multi-line magic comments like type: ignore within parentheses (#3740)
• Fix error in AST validation when Black removes trailing whitespace in a type comment (#3773)

Preview style

• Implicitly concatenated strings used as function args are no longer wrapped inside parentheses (#3640)
• Remove blank lines between a class definition and its docstring (#3692)

Configuration

• The --workers argument to Black can now be specified via the BLACK_NUM_WORKERS environment variable (#3743)
• .pytest_cache, .ruff_cache and .vscode are now excluded by default (#3691)
• Fix Black not honouring pyproject.toml settings when running --stdin-filename and the pyproject.toml found isn't in the current working directory (#3719)
• Black will now error if exclude and extend-exclude have invalid data types in pyproject.toml, instead of silently doing the wrong thing (#3764)

Packaging

• Upgrade mypyc from 0.991 to 1.3 (#3697)
• Remove patching of Click that mitigated errors on Python 3.6 with LANG=C (#3768)

Parser

• Add support for the new PEP 695 syntax in Python 3.12 (#3703)

Performance

• Speed up Black significantly when the cache is full (#3751)
• Avoid importing IPython in a case where we wouldn't need it (#3748)

Output

• Use aware UTC datetimes internally, avoids deprecation warning on Python 3.12 (#3728)
• Change verbose logging to exactly mirror Black's logic for source discovery (#3749)

Blackd

• The blackd argument parser now shows the default values for options in their help text (#3712)

Integrations

• Black is now tested with PYTHONWARNDEFAULTENCODING = 1 (#3763)
• Update GitHub Action to display black output in the job summary (#3688)

Documentation

• Add a CITATION.cff file to the root of the repository, containing metadata on how to cite this software (#3723)
• Update the classes and exceptions documentation in Developer reference to match the latest code base (#3755)

23.3.0

Highlights

This release fixes a longstanding confusing behavior in Black's GitHub action, where the version of the action did not determine the version of Black being run (issue #3382). In addition, there is a small bug fix around imports and a number of improvements to the preview style.

Please try out the preview style with black --preview and tell us your feedback. All changes in the preview style are expected to become part of Black's stable style in January 2024.

Stable style

• Import lines with # fmt: skip and # fmt: off no longer have an extra blank line added when they are right after another import line (#3610)

Preview style

• Add trailing commas to collection literals even if there's a comment after the last entry (#3393)
• async def, async for, and async with statements are now formatted consistently compared to their non-async version. (#3609)
• with statements that contain two context managers will be consistently wrapped in parentheses (#3589)
• Let string splitters respect East Asian Width (#3445)
• Now long string literals can be split after East Asian commas and periods (、 U+3001 IDEOGRAPHIC COMMA, 。 U+3002 IDEOGRAPHIC FULL STOP, & ， U+FF0C FULLWIDTH COMMA) besides before spaces (#3445)
• For stubs, enforce one blank line after a nested class with a body other than just ... (#3564)
• Improve handling of multiline strings by changing line split behavior (#1879)

Parser

• Added support for formatting files with invalid type comments (#3594)

Integrations

• Update GitHub Action to use the version of Black equivalent to action's version if version input is not specified (#3543)
• Fix missing Python binary path in autoload script for vim (#3508)

Documentation

• Document that only the most recent release is supported for security issues; vulnerabilities should be reported through Tidelift (#3612)

23.1.0

Highlights

This is the first release of 2023, and following our stability policy, it comes with a number of improvements to our stable style, including improvements to empty line handling, removal of redundant parentheses in several contexts, and output that highlights implicitly concatenated strings better.

There are also many changes to the preview style; try out black --preview and give us feedback to help us set the stable style for next year.

In addition to style changes, Black now automatically infers the supported Python versions from your pyproject.toml file, removing the need to set Black's target versions separately.

Stable style

• Introduce the 2023 stable style, which incorporates most aspects of last year's preview style (#3418). Specific changes:
  • Enforce empty lines before classes and functions with sticky leading comments (#3302) (22.12.0)
  • Reformat empty and whitespace-only files as either an empty file (if no newline is present) or as a single newline character (if a newline is present) (#3348) (22.12.0)
  • Implicitly concatenated strings used as function args are now wrapped inside parentheses (#3307) (22.12.0)
  • Correctly handle trailing commas that are inside a line's leading non-nested parens (#3370) (22.12.0)
  • --skip-string-normalization / -S now prevents docstring prefixes from being normalized as expected (#3168) (since 22.8.0)
  • When using --skip-magic-trailing-comma or -C, trailing commas are stripped from subscript expressions with more than 1 element (#3209) (22.8.0)
  • Implicitly concatenated strings inside a list, set, or tuple are now wrapped inside parentheses (#3162) (22.8.0)
  • Fix a string merging/split issue when a comment is present in the middle of implicitly concatenated strings on its own line (#3227) (22.8.0)
  • Docstring quotes are no longer moved if it would violate the line length limit (#3044, #3430) (22.6.0)
  • Parentheses around return annotations are now managed (#2990) (22.6.0)
  • Remove unnecessary parentheses around awaited objects (#2991) (22.6.0)
  • Remove unnecessary parentheses in with statements (#2926) (22.6.0)
  • Remove trailing newlines after code block open (#3035) (22.6.0)
  • Code cell separators #%% are now standardised to # %% (#2919) (22.3.0)
  • Remove unnecessary parentheses from except statements (#2939) (22.3.0)
  • Remove unnecessary parentheses from tuple unpacking in for loops (#2945) (22.3.0)
  • Avoid magic-trailing-comma in single-element subscripts (#2942) (22.3.0)
• Fix a crash when a colon line is marked between # fmt: off and # fmt: on (#3439)

Preview style

• Format hex codes in unicode escape sequences in string literals (#2916)
• Add parentheses around if-else expressions (#2278)
• Improve performance on large expressions that contain many strings (#3467)
• Fix a crash in preview style with assert + parenthesized string (#3415)
• Fix crashes in preview style with walrus operators used in function return annotations and except clauses (#3423)
• Fix a crash in preview advanced string processing where mixed implicitly concatenated regular and f-strings start with an empty span (#3463)
• Fix a crash in preview advanced string processing where a standalone comment is placed before a dict's value (#3469)
• Fix an issue where extra empty lines are added when a decorator has # fmt: skip applied or there is a standalone comment between decorators (#3470)
• Do not put the closing quotes in a docstring on a separate line, even if the line is too long (#3430)
• Long values in dict literals are now wrapped in parentheses; correspondingly unnecessary parentheses around short values in dict literals are now removed; long string lambda values are now wrapped in parentheses (#3440)
• Fix two crashes in preview style involving edge cases with docstrings (#3451)
• Exclude string type annotations from improved string processing; fix crash when the return type annotation is stringified and spans across multiple lines (#3462)
• Wrap multiple context managers in parentheses when targeting Python 3.9+ (#3489)
• Fix several crashes in preview style with walrus operators used in with statements or tuples (#3473)
• Fix an invalid quote escaping bug in f-string expressions where it produced invalid code. Implicitly concatenated f-strings with different quotes can now be merged or quote-normalized by changing the quotes used in expressions. (#3509)
• Fix crash on await (yield) when Black is compiled with mypyc (#3533)

Configuration

• Black now tries to infer its --target-version from the project metadata specified in pyproject.toml (#3219)

Packaging

• Upgrade mypyc from 0.971 to 0.991 so mypycified Black can be built on armv7 (#3380)
  • This also fixes some crashes while using compiled Black with a debug build of CPython
• Drop specific support for the tomli requirement on 3.11 alpha releases, working around a bug that would cause the requirement not to be installed on any non-final Python releases (#3448)
• Black now depends on packaging version 22.0 or later. This is required for new functionality that needs to parse part of the project metadata (#3219)

Output

• Calling black --help multiple times will return the same help contents each time (#3516)
• Verbose logging now shows the values of pyproject.toml configuration variables (#3392)
• Fix false symlink detection messages in verbose output due to using an incorrect relative path to the project root (#3385)

Integrations

• Move 3.11 CI to normal flow now that all dependencies support 3.11 (#3446)
• Docker: Add new latest_prerelease tag automation to follow latest black alpha release on docker images (#3465)

Documentation

• Expand vim-plug installation instructions to offer more explicit options (#3468)

22.12.0

Preview style

• Enforce empty lines before classes and functions with sticky leading comments (#3302)
• Reformat empty and whitespace-only files as either an empty file (if no newline is present) or as a single newline character (if a newline is present) (#3348)
• Implicitly concatenated strings used as function args are now wrapped inside parentheses (#3307)
• For assignment statements, prefer splitting the right hand side if the left hand side fits on a single line (#3368)
• Correctly handle trailing commas that are inside a line's leading non-nested parens (#3370)

Configuration

• Fix incorrectly applied .gitignore rules by considering the .gitignore location and the relative path to the target file (#3338)
• Fix incorrectly ignoring .gitignore presence when more than one source directory is specified (#3336)

Parser

• Parsing support has been added for walruses inside generator expression that are passed as function args (for example, any(match := my_re.match(text) for text in texts)) (#3327).

Integrations

• Vim plugin: Optionally allow using the system installation of Black via let g:black_use_virtualenv = 0(#3309)

22.10.0

Highlights

• Runtime support for Python 3.6 has been removed. Formatting 3.6 code will still be supported until further notice.

Stable style

• Fix a crash when # fmt: on is used on a different block level than # fmt: off (#3281)

Preview style

• Fix a crash when formatting some dicts with parenthesis-wrapped long string keys (#3262)

Configuration

• .ipynb_checkpoints directories are now excluded by default (#3293)
• Add --skip-source-first-line / -x option to ignore the first line of source code while formatting (#3299)

Packaging

• Executables made with PyInstaller will no longer crash when formatting several files at once on macOS. Native x86-64 executables for macOS are available once again. (#3275)
• Hatchling is now used as the build backend. This will not have any effect for users who install Black with its wheels from PyPI. (#3233)
• Faster compiled wheels are now available for CPython 3.11 (#3276)

Blackd

• Windows style (CRLF) newlines will be preserved (#3257).

Integrations

• Vim plugin: add flag (g:black_preview) to enable/disable the preview style (#3246)
• Update GitHub Action to support formatting of Jupyter Notebook files via a jupyter option (#3282)
• Update GitHub Action to support use of version specifiers (e.g. <23) for Black version (#3265)

22.8.0

Highlights

• Python 3.11 is now supported, except for blackd as aiohttp does not support 3.11 as of publishing (#3234)
• This is the last release that supports running Black on Python 3.6 (formatting 3.6 code will continue to be supported until further notice)
• Reword the stability policy to say that we may, in rare cases, make changes that affect code that was not previously formatted by Black (#3155)

Stable style

• Fix an infinite loop when using # fmt: on/off in the middle of an expression or code block (#3158)
• Fix incorrect handling of # fmt: skip on colon (:) lines (#3148)
• Comments are no longer deleted when a line had spaces removed around power operators (#2874)

Preview style

• Single-character closing docstring quotes are no longer moved to their own line as this is invalid. This was a bug introduced in version 22.6.0. (#3166)
• --skip-string-normalization / -S now prevents docstring prefixes from being normalized as expected (#3168)
• When using --skip-magic-trailing-comma or -C, trailing commas are stripped from subscript expressions with more than 1 element (#3209)
• Implicitly concatenated strings inside a list, set, or tuple are now wrapped inside parentheses (#3162)
• Fix a string merging/split issue when a comment is present in the middle of implicitly concatenated strings on its own line (#3227)

Blackd

• blackd now supports enabling the preview style via the X-Preview header (#3217)

Configuration

• Black now uses the presence of debug f-strings to detect target version (#3215)
• Fix misdetection of project root and verbose logging of sources in cases involving --stdin-filename (#3216)
• Immediate .gitignore files in source directories given on the command line are now also respected, previously only .gitignore files in the project root and automatically discovered directories were respected (#3237)

Documentation

• Recommend using BlackConnect in IntelliJ IDEs (#3150)

Integrations

• Vim plugin: prefix messages with Black: so it's clear they come from Black (#3194)
• Docker: changed to a /opt/venv installation + added to PATH to be available to non-root users (#3202)

Output

• Change from deprecated asyncio.get_event_loop() to create our event loop which removes DeprecationWarning (#3164)
• Remove logging from internal blib2to3 library since it regularly emits error logs about failed caching that can and should be ignored (#3193)

Parser

• Type comments are now included in the AST equivalence check consistently so accidental deletion raises an error. Though type comments can't be tracked when running on PyPy 3.7 due to standard library limitations. (#2874)

Performance

• Reduce Black's startup time when formatting a single file by 15-30% (#3211)

22.6.0

Style

• Fix unstable formatting involving #fmt: skip and # fmt:skip comments (notice the lack of spaces) (#2970)

Preview style

• Docstring quotes are no longer moved if it would violate the line length limit (#3044)
• Parentheses around return annotations are now managed (#2990)
• Remove unnecessary parentheses around awaited objects (#2991)
• Remove unnecessary parentheses in with statements (#2926)
• Remove trailing newlines after code block open (#3035)

Integrations

• Add scripts/migrate-black.py script to ease introduction of Black to a Git project (#3038)

Output

• Output Python version and implementation as part of --version flag (#2997)

Packaging

• Use tomli instead of tomllib on Python 3.11 builds where tomllib is not available (#2987)

Parser

• PEP 654 syntax (for example, except *ExceptionGroup:) is now supported (#3016)
• PEP 646 syntax (for example, Array[Batch, *Shape] or def fn(*args: *T) -> None) is now supported (#3071)

Vim Plugin

• Fix strtobool function. It didn't parse true/on/false/off. (#3025)

22.3.0

Preview style

• Code cell separators #%% are now standardised to # %% (#2919)
• Remove unnecessary parentheses from except statements (#2939)
• Remove unnecessary parentheses from tuple unpacking in for loops (#2945)
• Avoid magic-trailing-comma in single-element subscripts (#2942)

Configuration

• Do not format __pypackages__ directories by default (#2836)
• Add support for specifying stable version with --required-version (#2832).
• Avoid crashing when the user has no homedir (#2814)
• Avoid crashing when md5 is not available (#2905)
• Fix handling of directory junctions on Windows (#2904)

Documentation

• Update pylint config documentation (#2931)

Integrations

• Move test to disable plugin in Vim/Neovim, which speeds up loading (#2896)

Output

• In verbose mode, log when Black is using user-level config (#2861)

Packaging

• Fix Black to work with Click 8.1.0 (#2966)
• On Python 3.11 and newer, use the standard library's tomllib instead of tomli (#2903)
• black-primer, the deprecated internal devtool, has been removed and copied to a separate repository (#2924)

Parser

• Black can now parse starred expressions in the target of for and async for statements, e.g for item in *items_1, *items_2: pass (#2879).

22.1.0

At long last, Black is no longer a beta product! This is the first non-beta release and the first release covered by our new stability policy.

Highlights

• Remove Python 2 support (#2740)
• Introduce the --preview flag (#2752)

Style

• Deprecate --experimental-string-processing and move the functionality under --preview (#2789)
• For stubs, one blank line between class attributes and methods is now kept if there's at least one pre-existing blank line (#2736)
• Black now normalizes string prefix order (#2297)
• Remove spaces around power operators if both operands are simple (#2726)
• Work around bug that causes unstable formatting in some cases in the presence of the magic trailing comma (#2807)
• Use parentheses for attribute access on decimal float and int literals (#2799)
• Don't add whitespace for attribute access on hexadecimal, binary, octal, and complex literals (#2799)
• Treat blank lines in stubs the same inside top-level if statements (#2820)
• Fix unstable formatting with semicolons and arithmetic expressions (#2817)
• Fix unstable formatting around magic trailing comma (#2572)

Parser

• Fix mapping cases that contain as-expressions, like case {"key": 1 | 2 as password} (#2686)
• Fix cases that contain multiple top-level as-expressions, like case 1 as a, 2 as b (#2716)
• Fix call patterns that contain as-expressions with keyword arguments, like case Foo(bar=baz as quux) (#2749)
• Tuple unpacking on return and yield constructs now implies 3.8+ (#2700)
• Unparenthesized tuples on annotated assignments (e.g values: Tuple[int, ...] = 1, 2, 3) now implies 3.8+ (#2708)
• Fix handling of standalone match() or case() when there is a trailing newline or a comment inside of the parentheses. (#2760)
• from __future__ import annotations statement now implies Python 3.7+ (#2690)

Performance

• Speed-up the new backtracking parser about 4X in general (enabled when --target-version is set to 3.10 and higher). (#2728)
• Black is now compiled with mypyc for an overall 2x speed-up. 64-bit Windows, MacOS, and Linux (not including musl) are supported. (#1009, #2431)

Configuration

• Do not accept bare carriage return line endings in pyproject.toml (#2408)
• Add configuration option (python-cell-magics) to format cells with custom magics in Jupyter Notebooks (#2744)
• Allow setting custom cache directory on all platforms with environment variable BLACK_CACHE_DIR (#2739).
• Enable Python 3.10+ by default, without any extra need to specify --target-version=py310. (#2758)
• Make passing SRC or --code mandatory and mutually exclusive (#2804)

Output

• Improve error message for invalid regular expression (#2678)
• Improve error message when parsing fails during AST safety check by embedding the underlying SyntaxError (#2693)
• No longer color diff headers white as it's unreadable in light themed terminals (#2691)
• Text coloring added in the final statistics (#2712)
• Verbose mode also now describes how a project root was discovered and which paths will be formatted. (#2526)

Packaging

• All upper version bounds on dependencies have been removed (#2718)
• typing-extensions is no longer a required dependency in Python 3.10+ (#2772)
• Set click lower bound to 8.0.0 (#2791)

Integrations

• Update GitHub action to support containerized runs (#2748)

Documentation

• Change protocol in pip installation instructions to https:// (#2761)
• Change HTML theme to Furo primarily for its responsive design and mobile support (#2793)
• Deprecate the black-primer tool (#2809)
• Document Python support policy (#2819)

21.12b0

Black

• Fix determination of f-string expression spans (#2654)
• Fix bad formatting of error messages about EOF in multi-line statements (#2343)
• Functions and classes in blocks now have more consistent surrounding spacing (#2472)

Jupyter Notebook support

• Cell magics are now only processed if they are known Python cell magics. Earlier, all cell magics were tokenized, leading to possible indentation errors e.g. with %%writefile. (#2630)
• Fix assignment to environment variables in Jupyter Notebooks (#2642)

Python 3.10 support

• Point users to using --target-version py310 if we detect 3.10-only syntax (#2668)
• Fix match statements with open sequence subjects, like match a, b: or match a, *b: (#2639) (#2659)
• Fix match/case statements that contain match/case soft keywords multiple times, like match re.match() (#2661)
• Fix case statements with an inline body (#2665)
• Fix styling of starred expressions inside match subject (#2667)
• Fix parser error location on invalid syntax in a match statement (#2649)
• Fix Python 3.10 support on platforms without ProcessPoolExecutor (#2631)
• Improve parsing performance on code that uses match under --target-version py310 up to ~50% (#2670)

Packaging

• Remove dependency on regex (#2644) (#2663)

21.11b1

Black

• Bumped regex version minimum to 2021.4.4 to fix Pattern class usage (#2621)

21.11b0

Black

• Warn about Python 2 deprecation in more cases by improving Python 2 only syntax detection (#2592)
• Add experimental PyPy support (#2559)
• Add partial support for the match statement. As it's experimental, it's only enabled when --target-version py310 is explicitly specified (#2586)
• Add support for parenthesized with (#2586)
• Declare support for Python 3.10 for running Black (#2562)

Integrations

• Fixed vim plugin with Python 3.10 by removing deprecated distutils import (#2610)
• The vim plugin now parses skip_magic_trailing_comma from pyproject.toml (#2613)

21.10b0

Black

• Document stability policy, that will apply for non-beta releases (#2529)
• Add new --workers parameter (#2514)
• Fixed feature detection for positional-only arguments in lambdas (#2532)
• Bumped typed-ast version minimum to 1.4.3 for 3.10 compatibility (#2519)
• Fixed a Python 3.10 compatibility issue where the loop argument was still being passed even though it has been removed (#2580)
• Deprecate Python 2 formatting support (#2523)

Blackd

• Remove dependency on aiohttp-cors (#2500)
• Bump required aiohttp version to 3.7.4 (#2509)

Black-Primer

• Add primer support for --projects (#2555)
• Print primer summary after individual failures (#2570)

Integrations

• Allow to pass target_version in the vim plugin (#1319)
• Install build tools in docker file and use multi-stage build to keep the image size down (#2582)

21.9b0

Packaging

• Fix missing modules in self-contained binaries (#2466)
• Fix missing toml extra used during installation (#2475)

21.8b0

Black

• Add support for formatting Jupyter Notebook files (#2357)
• Move from appdirs dependency to platformdirs (#2375)
• Present a more user-friendly error if .gitignore is invalid (#2414)
• The failsafe for accidentally added backslashes in f-string expressions has been hardened to handle more edge cases during quote normalization (#2437)
• Avoid changing a function return type annotation's type to a tuple by adding a trailing comma (#2384)
• Parsing support has been added for unparenthesized walruses in set literals, set comprehensions, and indices (#2447).
• Pin setuptools-scm build-time dependency version (#2457)
• Exclude typing-extensions version 3.10.0.1 due to it being broken on Python 3.10 (#2460)

Blackd

• Replace sys.exit(-1) with raise ImportError as it plays more nicely with tools that scan installed packages (#2440)

Integrations

• The provided pre-commit hooks no longer specify language_version to avoid overriding default_language_version (#2430)

21.7b0

Black

• Configuration files using TOML features higher than spec v0.5.0 are now supported (#2301)
• Add primer support and test for code piped into black via STDIN (#2315)
• Fix internal error when FORCE_OPTIONAL_PARENTHESES feature is enabled (#2332)
• Accept empty stdin (#2346)
• Provide a more useful error when parsing fails during AST safety checks (#2304)

Docker

• Add new latest_release tag automation to follow latest black release on docker images (#2374)

Integrations

• The vim plugin now searches upwards from the directory containing the current buffer instead of the current working directory for pyproject.toml. (#1871)
• The vim plugin now reads the correct string normalization option in pyproject.toml (#1869)
• The vim plugin no longer crashes Black when there's boolean values in pyproject.toml (#1869)

21.6b0

Black

• Fix failure caused by fmt: skip and indentation (#2281)
• Account for += assignment when deciding whether to split string (#2312)
• Correct max string length calculation when there are string operators (#2292)
• Fixed option usage when using the --code flag (#2259)
• Do not call uvloop.install() when Black is used as a library (#2303)
• Added --required-version option to require a specific version to be running (#2300)
• Fix incorrect custom breakpoint indices when string group contains fake f-strings (#2311)
• Fix regression where R prefixes would be lowercased for docstrings (#2285)
• Fix handling of named escapes (\N{...}) when --experimental-string-processing is used (#2319)

Integrations

• The official Black action now supports choosing what version to use, and supports the major 3 OSes. (#1940)

21.5b2

Black

• A space is no longer inserted into empty docstrings (#2249)
• Fix handling of .gitignore files containing non-ASCII characters on Windows (#2229)
• Respect .gitignore files in all levels, not only root/.gitignore file (apply .gitignore rules like git does) (#2225)
• Restored compatibility with Click 8.0 on Python 3.6 when LANG=C used (#2227)
• Add extra uvloop install + import support if in python env (#2258)
• Fix --experimental-string-processing crash when matching parens are not found (#2283)
• Make sure to split lines that start with a string operator (#2286)
• Fix regular expression that black uses to identify f-expressions (#2287)

Blackd

• Add a lower bound for the aiohttp-cors dependency. Only 0.4.0 or higher is supported. (#2231)

Packaging

• Release self-contained x86_64 MacOS binaries as part of the GitHub release pipeline (#2198)
• Always build binaries with the latest available Python (#2260)

Documentation

• Add discussion of magic comments to FAQ page (#2272)
• --experimental-string-processing will be enabled by default in the future (#2273)
• Fix typos discovered by codespell (#2228)
• Fix Vim plugin installation instructions. (#2235)
• Add new Frequently Asked Questions page (#2247)
• Fix encoding + symlink issues preventing proper build on Windows (#2262)

21.5b1

Black

• Refactor src/black/__init__.py into many files (#2206)

Documentation

• Replaced all remaining references to the master branch with the main branch. Some additional changes in the source code were also made. (#2210)
• Significantly reorganized the documentation to make much more sense. Check them out by heading over to the stable docs on RTD. (#2174)

21.5b0

Black

• Set --pyi mode if --stdin-filename ends in .pyi (#2169)
• Stop detecting target version as Python 3.9+ with pre-PEP-614 decorators that are being called but with no arguments (#2182)

Black-Primer

• Add --no-diff to black-primer to suppress formatting changes (#2187)

21.4b2

Black

• Fix crash if the user configuration directory is inaccessible. (#2158)

• Clarify circumstances in which Black may change the AST (#2159)

• Allow .gitignore rules to be overridden by specifying exclude in pyproject.toml or on the command line. (#2170)

Packaging

• Install primer.json (used by black-primer by default) with black. (#2154)

21.4b1

Black

• Fix crash on docstrings ending with "\ ". (#2142)

• Fix crash when atypical whitespace is cleaned out of dostrings (#2120)

• Reflect the --skip-magic-trailing-comma and --experimental-string-processing flags in the name of the cache file. Without this fix, changes in these flags would not take effect if the cache had already been populated. (#2131)

• Don't remove necessary parentheses from assignment expression containing assert / return statements. (#2143)

Packaging

• Bump pathspec to >= 0.8.1 to solve invalid .gitignore exclusion handling

21.4b0

Black

• Fixed a rare but annoying formatting instability created by the combination of optional trailing commas inserted by Black and optional parentheses looking at pre-existing "magic" trailing commas. This fixes issue #1629 and all of its many many duplicates. (#2126)

• Black now processes one-line docstrings by stripping leading and trailing spaces, and adding a padding space when needed to break up """". (#1740)

• Black now cleans up leading non-breaking spaces in comments (#2092)

• Black now respects --skip-string-normalization when normalizing multiline docstring quotes (#1637)

• Black no longer removes all empty lines between non-function code and decorators when formatting typing stubs. Now Black enforces a single empty line. (#1646)

• Black no longer adds an incorrect space after a parenthesized assignment expression in if/while statements (#1655)

• Added --skip-magic-trailing-comma / -C to avoid using trailing commas as a reason to split lines (#1824)

• fixed a crash when PWD=/ on POSIX (#1631)

• fixed "I/O operation on closed file" when using --diff (#1664)

• Prevent coloured diff output being interleaved with multiple files (#1673)

• Added support for PEP 614 relaxed decorator syntax on python 3.9 (#1711)

• Added parsing support for unparenthesized tuples and yield expressions in annotated assignments (#1835)

• added --extend-exclude argument (PR #2005)

• speed up caching by avoiding pathlib (#1950)

• --diff correctly indicates when a file doesn't end in a newline (#1662)

• Added --stdin-filename argument to allow stdin to respect --force-exclude rules (#1780)

• Lines ending with fmt: skip will now be not formatted (#1800)

• PR #2053: Black no longer relies on typed-ast for Python 3.8 and higher

• PR #2053: Python 2 support is now optional, install with python3 -m pip install black[python2] to maintain support.

• Exclude venv directory by default (#1683)

• Fixed "Black produced code that is not equivalent to the source" when formatting Python 2 docstrings (#2037)

Packaging

• Self-contained native Black binaries are now provided for releases via GitHub Releases (#1743)

20.8b1

Packaging

• explicitly depend on Click 7.1.2 or newer as Black no longer works with versions older than 7.0

20.8b0

Black

• re-implemented support for explicit trailing commas: now it works consistently within any bracket pair, including nested structures (#1288 and duplicates)

• Black now reindents docstrings when reindenting code around it (#1053)

• Black now shows colored diffs (#1266)

• Black is now packaged using 'py3' tagged wheels (#1388)

• Black now supports Python 3.8 code, e.g. star expressions in return statements (#1121)

• Black no longer normalizes capital R-string prefixes as those have a community-accepted meaning (#1244)

• Black now uses exit code 2 when specified configuration file doesn't exit (#1361)

• Black now works on AWS Lambda (#1141)

• added --force-exclude argument (#1032)

• removed deprecated --py36 option (#1236)

• fixed --diff output when EOF is encountered (#526)

• fixed # fmt: off handling around decorators (#560)

• fixed unstable formatting with some # type: ignore comments (#1113)

• fixed invalid removal on organizing brackets followed by indexing (#1575)

• introduced black-primer, a CI tool that allows us to run regression tests against existing open source users of Black (#1402)

• introduced property-based fuzzing to our test suite based on Hypothesis and Hypothersmith (#1566)

• implemented experimental and disabled by default long string rewrapping (#1132), hidden under a --experimental-string-processing flag while it's being worked on; this is an undocumented and unsupported feature, you lose Internet points for depending on it (#1609)

Vim plugin

• prefer virtualenv packages over global packages (#1383)

19.10b0

• added support for PEP 572 assignment expressions (#711)

• added support for PEP 570 positional-only arguments (#943)

• added support for async generators (#593)

• added support for pre-splitting collections by putting an explicit trailing comma inside (#826)

• added black -c as a way to format code passed from the command line (#761)

• --safe now works with Python 2 code (#840)

• fixed grammar selection for Python 2-specific code (#765)

• fixed feature detection for trailing commas in function definitions and call sites (#763)

• # fmt: off/# fmt: on comment pairs placed multiple times within the same block of code now behave correctly (#1005)

• Black no longer crashes on Windows machines with more than 61 cores (#838)

• Black no longer crashes on standalone comments prepended with a backslash (#767)

• Black no longer crashes on from ... import blocks with comments (#829)

• Black no longer crashes on Python 3.7 on some platform configurations (#494)

• Black no longer fails on comments in from-imports (#671)

• Black no longer fails when the file starts with a backslash (#922)

• Black no longer merges regular comments with type comments (#1027)

• Black no longer splits long lines that contain type comments (#997)

• removed unnecessary parentheses around yield expressions (#834)

• added parentheses around long tuples in unpacking assignments (#832)

• added parentheses around complex powers when they are prefixed by a unary operator (#646)

• fixed bug that led Black format some code with a line length target of 1 (#762)

• Black no longer introduces quotes in f-string subexpressions on string boundaries (#863)

• if Black puts parenthesis around a single expression, it moves comments to the wrapped expression instead of after the brackets (#872)

• blackd now returns the version of Black in the response headers (#1013)

• blackd can now output the diff of formats on source code when the X-Diff header is provided (#969)

19.3b0

• new option --target-version to control which Python versions Black-formatted code should target (#618)

• deprecated --py36 (use --target-version=py36 instead) (#724)

• Black no longer normalizes numeric literals to include _ separators (#696)

• long del statements are now split into multiple lines (#698)

• type comments are no longer mangled in function signatures

• improved performance of formatting deeply nested data structures (#509)

• Black now properly formats multiple files in parallel on Windows (#632)

• Black now creates cache files atomically which allows it to be used in parallel pipelines (like xargs -P8) (#673)

• Black now correctly indents comments in files that were previously formatted with tabs (#262)

• blackd now supports CORS (#622)

18.9b0

• numeric literals are now formatted by Black (#452, #461, #464, #469):

  • numeric literals are normalized to include _ separators on Python 3.6+ code

  • added --skip-numeric-underscore-normalization to disable the above behavior and leave numeric underscores as they were in the input

  • code with _ in numeric literals is recognized as Python 3.6+

  • most letters in numeric literals are lowercased (e.g., in 1e10, 0x01)

  • hexadecimal digits are always uppercased (e.g. 0xBADC0DE)

• added blackd, see its documentation for more info (#349)

• adjacent string literals are now correctly split into multiple lines (#463)

• trailing comma is now added to single imports that don't fit on a line (#250)

• cache is now populated when --check is successful for a file which speeds up consecutive checks of properly formatted unmodified files (#448)

• whitespace at the beginning of the file is now removed (#399)

• fixed mangling pweave and Spyder IDE special comments (#532)

• fixed unstable formatting when unpacking big tuples (#267)

• fixed parsing of __future__ imports with renames (#389)

• fixed scope of # fmt: off when directly preceding yield and other nodes (#385)

• fixed formatting of lambda expressions with default arguments (#468)

• fixed async for statements: Black no longer breaks them into separate lines (#372)

• note: the Vim plugin stopped registering ,= as a default chord as it turned out to be a bad idea (#415)

18.6b4

• hotfix: don't freeze when multiple comments directly precede # fmt: off (#371)

18.6b3

• typing stub files (.pyi) now have blank lines added after constants (#340)

• # fmt: off and # fmt: on are now much more dependable:

  • they now work also within bracket pairs (#329)

  • they now correctly work across function/class boundaries (#335)

  • they now work when an indentation block starts with empty lines or misaligned comments (#334)

• made Click not fail on invalid environments; note that Click is right but the likelihood we'll need to access non-ASCII file paths when dealing with Python source code is low (#277)

• fixed improper formatting of f-strings with quotes inside interpolated expressions (#322)

• fixed unnecessary slowdown when long list literals where found in a file

• fixed unnecessary slowdown on AST nodes with very many siblings

• fixed cannibalizing backslashes during string normalization

• fixed a crash due to symbolic links pointing outside of the project directory (#338)

18.6b2

• added --config (#65)

• added -h equivalent to --help (#316)

• fixed improper unmodified file caching when -S was used

• fixed extra space in string unpacking (#305)

• fixed formatting of empty triple quoted strings (#313)

• fixed unnecessary slowdown in comment placement calculation on lines without comments

18.6b1

• hotfix: don't output human-facing information on stdout (#299)

• hotfix: don't output cake emoji on non-zero return code (#300)

18.6b0

• added --include and --exclude (#270)

• added --skip-string-normalization (#118)

• added --verbose (#283)

• the header output in --diff now actually conforms to the unified diff spec

• fixed long trivial assignments being wrapped in unnecessary parentheses (#273)

• fixed unnecessary parentheses when a line contained multiline strings (#232)

• fixed stdin handling not working correctly if an old version of Click was used (#276)

• Black now preserves line endings when formatting a file in place (#258)

18.5b1

• added --pyi (#249)

• added --py36 (#249)

• Python grammar pickle caches are stored with the formatting caches, making Black work in environments where site-packages is not user-writable (#192)

• Black now enforces a PEP 257 empty line after a class-level docstring (and/or fields) and the first method

• fixed invalid code produced when standalone comments were present in a trailer that was omitted from line splitting on a large expression (#237)

• fixed optional parentheses being removed within # fmt: off sections (#224)

• fixed invalid code produced when stars in very long imports were incorrectly wrapped in optional parentheses (#234)

• fixed unstable formatting when inline comments were moved around in a trailer that was omitted from line splitting on a large expression (#238)

• fixed extra empty line between a class declaration and the first method if no class docstring or fields are present (#219)

• fixed extra empty line between a function signature and an inner function or inner class (#196)

18.5b0

• call chains are now formatted according to the fluent interfaces style (#67)

• data structure literals (tuples, lists, dictionaries, and sets) are now also always exploded like imports when they don't fit in a single line (#152)

• slices are now formatted according to PEP 8 (#178)

• parentheses are now also managed automatically on the right-hand side of assignments and return statements (#140)

• math operators now use their respective priorities for delimiting multiline expressions (#148)

• optional parentheses are now omitted on expressions that start or end with a bracket and only contain a single operator (#177)

• empty parentheses in a class definition are now removed (#145, #180)

• string prefixes are now standardized to lowercase and u is removed on Python 3.6+ only code and Python 2.7+ code with the unicode_literals future import (#188, #198, #199)

• typing stub files (.pyi) are now formatted in a style that is consistent with PEP 484 (#207, #210)

• progress when reformatting many files is now reported incrementally

• fixed trailers (content with brackets) being unnecessarily exploded into their own lines after a dedented closing bracket (#119)

• fixed an invalid trailing comma sometimes left in imports (#185)

• fixed non-deterministic formatting when multiple pairs of removable parentheses were used (#183)

• fixed multiline strings being unnecessarily wrapped in optional parentheses in long assignments (#215)

• fixed not splitting long from-imports with only a single name

• fixed Python 3.6+ file discovery by also looking at function calls with unpacking. This fixed non-deterministic formatting if trailing commas where used both in function signatures with stars and function calls with stars but the former would be reformatted to a single line.

• fixed crash on dealing with optional parentheses (#193)

• fixed "is", "is not", "in", and "not in" not considered operators for splitting purposes

• fixed crash when dead symlinks where encountered

18.4a4

• don't populate the cache on --check (#175)

18.4a3

• added a "cache"; files already reformatted that haven't changed on disk won't be reformatted again (#109)

• --check and --diff are no longer mutually exclusive (#149)

• generalized star expression handling, including double stars; this fixes multiplication making expressions "unsafe" for trailing commas (#132)

• Black no longer enforces putting empty lines behind control flow statements (#90)

• Black now splits imports like "Mode 3 + trailing comma" of isort (#127)

• fixed comment indentation when a standalone comment closes a block (#16, #32)

• fixed standalone comments receiving extra empty lines if immediately preceding a class, def, or decorator (#56, #154)

• fixed --diff not showing entire path (#130)

• fixed parsing of complex expressions after star and double stars in function calls (#2)

• fixed invalid splitting on comma in lambda arguments (#133)

• fixed missing splits of ternary expressions (#141)

18.4a2

• fixed parsing of unaligned standalone comments (#99, #112)

• fixed placement of dictionary unpacking inside dictionary literals (#111)

• Vim plugin now works on Windows, too

• fixed unstable formatting when encountering unnecessarily escaped quotes in a string (#120)

18.4a1

• added --quiet (#78)

• added automatic parentheses management (#4)

• added pre-commit integration (#103, #104)

• fixed reporting on --check with multiple files (#101, #102)

• fixed removing backslash escapes from raw strings (#100, #105)

18.4a0

• added --diff (#87)

• add line breaks before all delimiters, except in cases like commas, to better comply with PEP 8 (#73)

• standardize string literals to use double quotes (almost) everywhere (#75)

• fixed handling of standalone comments within nested bracketed expressions; Black will no longer produce super long lines or put all standalone comments at the end of the expression (#22)

• fixed 18.3a4 regression: don't crash and burn on empty lines with trailing whitespace (#80)

• fixed 18.3a4 regression: # yapf: disable usage as trailing comment would cause Black to not emit the rest of the file (#95)

• when CTRL+C is pressed while formatting many files, Black no longer freaks out with a flurry of asyncio-related exceptions

• only allow up to two empty lines on module level and only single empty lines within functions (#74)

18.3a4

• # fmt: off and # fmt: on are implemented (#5)

• automatic detection of deprecated Python 2 forms of print statements and exec statements in the formatted file (#49)

• use proper spaces for complex expressions in default values of typed function arguments (#60)

• only return exit code 1 when --check is used (#50)

• don't remove single trailing commas from square bracket indexing (#59)

• don't omit whitespace if the previous factor leaf wasn't a math operator (#55)

• omit extra space in kwarg unpacking if it's the first argument (#46)

• omit extra space in Sphinx auto-attribute comments (#68)

18.3a3

• don't remove single empty lines outside of bracketed expressions (#19)

• added ability to pipe formatting from stdin to stdin (#25)

• restored ability to format code with legacy usage of async as a name (#20, #42)

• even better handling of numpy-style array indexing (#33, again)

18.3a2

• changed positioning of binary operators to occur at beginning of lines instead of at the end, following a recent change to PEP 8 (#21)

• ignore empty bracket pairs while splitting. This avoids very weirdly looking formattings (#34, #35)

• remove a trailing comma if there is a single argument to a call

• if top level functions were separated by a comment, don't put four empty lines after the upper function

• fixed unstable formatting of newlines with imports

• fixed unintentional folding of post scriptum standalone comments into last statement if it was a simple statement (#18, #28)

• fixed missing space in numpy-style array indexing (#33)

• fixed spurious space after star-based unary expressions (#31)

18.3a1

• added --check

• only put trailing commas in function signatures and calls if it's safe to do so. If the file is Python 3.6+ it's always safe, otherwise only safe if there are no *args or **kwargs used in the signature or call. (#8)

• fixed invalid spacing of dots in relative imports (#6, #13)

• fixed invalid splitting after comma on unpacked variables in for-loops (#23)

• fixed spurious space in parenthesized set expressions (#7)

• fixed spurious space after opening parentheses and in default arguments (#14, #17)

• fixed spurious space after unary operators when the operand was a complex expression (#15)

18.3a0

• first published version, Happy 🍰 Day 2018!

• alpha quality

• date-versioned (see: https://calver.org/)