-
+
+
<h2 align="center">The Uncompromising Code Formatter</h2>
<p align="center">
-<a href="https://travis-ci.org/ambv/black"><img alt="Build Status" src="https://travis-ci.org/ambv/black.svg?branch=master"></a>
+<a href="https://travis-ci.com/psf/black"><img alt="Build Status" src="https://travis-ci.com/psf/black.svg?branch=master"></a>
+<a href="https://github.com/psf/black/actions"><img alt="Actions Status" src="https://github.com/psf/black/workflows/Test/badge.svg"></a>
<a href="https://black.readthedocs.io/en/stable/?badge=stable"><img alt="Documentation Status" src="https://readthedocs.org/projects/black/badge/?version=stable"></a>
-<a href="https://coveralls.io/github/ambv/black?branch=master"><img alt="Coverage Status" src="https://coveralls.io/repos/github/ambv/black/badge.svg?branch=master"></a>
-<a href="https://github.com/
ambv/black/blob/master/LICENSE"><img alt="License: MIT" src="https://black.readthedocs.io/en/stable/_static/license.svg"></a>
-<a href="https://pypi.org/project/black/"><img alt="PyPI" src="https://black.readthedocs.io/en/stable/_static/pypi.svg"></a>
+<a href="https://coveralls.io/github/psf/black?branch=master"><img alt="Coverage Status" src="https://coveralls.io/repos/github/psf/black/badge.svg?branch=master"></a>
+<a href="https://github.com/
psf/black/blob/master/LICENSE"><img alt="License: MIT" src="https://black.readthedocs.io/en/stable/_static/license.svg"></a>
+<a href="https://pypi.org/project/black/"><img alt="PyPI" src="https://img.shields.io/pypi/v/black"></a>
<a href="https://pepy.tech/project/black"><img alt="Downloads" src="https://pepy.tech/badge/black"></a>
-<a href="https://github.com/
ambv/black"><img alt="Code style: black" src="https://img.shields.io/badge/code%20style-black-000000.svg"></a>
+<a href="https://github.com/
psf/black"><img alt="Code style: black" src="https://img.shields.io/badge/code%20style-black-000000.svg"></a>
</p>
> “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.
-*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.
+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.
+_Black_ makes code review faster by producing the smallest diffs possible.
-Try it out now using the [Black Playground](https://black.now.sh).
+Try it out now using the [Black Playground](https://black.now.sh). Watch the
+[PyCon 2019 talk](https://youtu.be/esZLCuWs_2Y) to learn more.
---
-*Contents:* **[Installation and usage](#installation-and-usage)** |
-**[Code style](#the-black-code-style)** |
-**[pyproject.toml](#pyprojecttoml)** |
-**[Editor integration](#editor-integration)** |
-**[blackd](#blackd)** |
+_Contents:_ **[Installation and usage](#installation-and-usage)** |
+**[Code style](#the-black-code-style)** | **[Pragmatism](#pragmatism)** |
+**[pyproject.toml](#pyprojecttoml)** | **[Editor integration](#editor-integration)** |
+**[blackd](#blackd)** | **[black-primer](#black-primer)** |
**[Version control integration](#version-control-integration)** |
-**[Ignoring unmodified files](#ignoring-unmodified-files)** |
-**[Testimonials](#testimonials)** |
-**[Show your style](#show-your-style)** |
-**[Contributing](#contributing-to-black)** |
-**[Change Log](#change-log)** |
+**[Ignoring unmodified files](#ignoring-unmodified-files)** | **[Used by](#used-by)** |
+**[Testimonials](#testimonials)** | **[Show your style](#show-your-style)** |
+**[Contributing](#contributing-to-black)** | **[Change Log](#change-log)** |
**[Authors](#authors)**
---
### Installation
-*Black* can be installed by running `pip install black`. It requires
-Python 3.6.0+ to run but you can reformat Python 2 code with it, too.
-
+_Black_ can be installed by running `pip install black`. It requires Python 3.6.0+ to
+run but you can reformat Python 2 code with it, too.
### Usage
To get started right away with sensible defaults:
-```
+```sh
black {source_file_or_directory}
```
### Command line options
-*Black* doesn't provide many options. You can list them by running
-`black --help`:
+_Black_ doesn't provide many options. You can list them by running `black --help`:
```text
-black [OPTIONS] [SRC]...
+Usage: black [OPTIONS] [SRC]...
+
+ The uncompromising code formatter.
Options:
- -l, --line-length INTEGER Where to wrap around. [default: 88]
- --py36 Allow using Python 3.6-only syntax on all input
- files. This will put trailing commas in function
- signatures and calls also after *args and
- **kwargs. [default: per-file auto-detection]
- --pyi Format all input files like typing stubs
- regardless of file extension (useful when piping
- source on standard input).
+ -c, --code TEXT Format the code passed in as a string.
+ -l, --line-length INTEGER How many characters per line to allow.
+ [default: 88]
+
+ -t, --target-version [py27|py33|py34|py35|py36|py37|py38]
+ Python versions that should be supported by
+ Black's output. [default: per-file auto-
+ detection]
+
+ --pyi Format all input files like typing stubs
+ regardless of file extension (useful when
+ piping source on standard input).
+
-S, --skip-string-normalization
- Don't normalize string quotes or prefixes.
- -N, --skip-numeric-underscore-normalization
- Don't normalize underscores in numeric literals.
- --check Don't write the files back, just return the
- status. Return code 0 means nothing would
- change. Return code 1 means some files would be
- reformatted. Return code 123 means there was an
- internal error.
- --diff Don't write the files back, just output a diff
- for each file on stdout.
- --fast / --safe If --fast given, skip temporary sanity checks.
- [default: --safe]
- --include TEXT A regular expression that matches files and
- directories that should be included on
- recursive searches. On Windows, use forward
- slashes for directories. [default: \.pyi?$]
- --exclude TEXT A regular expression that matches files and
- directories that should be excluded on
- recursive searches. On Windows, use forward
- slashes for directories. [default:
- build/|buck-out/|dist/|_build/|\.eggs/|\.git/|
- \.hg/|\.mypy_cache/|\.nox/|\.tox/|\.venv/]
- -q, --quiet Don't emit non-error messages to stderr. Errors
- are still emitted, silence those with
- 2>/dev/null.
- -v, --verbose Also emit messages to stderr about files
- that were not changed or were ignored due to
- --exclude=.
- --version Show the version and exit.
- --config PATH Read configuration from PATH.
- --help Show this message and exit.
+ Don't normalize string quotes or prefixes.
+ --check Don't write the files back, just return the
+ status. Return code 0 means nothing would
+ change. Return code 1 means some files
+ would be reformatted. Return code 123 means
+ there was an internal error.
+
+ --diff Don't write the files back, just output a
+ diff for each file on stdout.
+
+ --color / --no-color Show colored diff. Only applies when
+ `--diff` is given.
+
+ --fast / --safe If --fast given, skip temporary sanity
+ checks. [default: --safe]
+
+ --include TEXT A regular expression that matches files and
+ directories that should be included on
+ recursive searches. An empty value means
+ all files are included regardless of the
+ name. Use forward slashes for directories
+ on all platforms (Windows, too). Exclusions
+ are calculated first, inclusions later.
+ [default: \.pyi?$]
+
+ --exclude TEXT A regular expression that matches files and
+ directories that should be excluded on
+ recursive searches. An empty value means no
+ paths are excluded. Use forward slashes for
+ directories on all platforms (Windows, too).
+ Exclusions are calculated first, inclusions
+ later. [default: /(\.eggs|\.git|\.hg|\.mypy
+ _cache|\.nox|\.tox|\.venv|\.svn|_build|buck-
+ out|build|dist)/]
+
+ --force-exclude TEXT Like --exclude, but files and directories
+ matching this regex will be excluded even
+ when they are passed explicitly as arguments
+
+ -q, --quiet Don't emit non-error messages to stderr.
+ Errors are still emitted; silence those with
+ 2>/dev/null.
+
+ -v, --verbose Also emit messages to stderr about files
+ that were not changed or were ignored due to
+ --exclude=.
+
+ --version Show the version and exit.
+ --config FILE Read configuration from PATH.
+ -h, --help Show this message and exit.
```
-*Black* is a well-behaved Unix-style command-line tool:
-* it does nothing if no sources are passed to it;
-* it will read from standard input and write to standard output if `-`
- is used as the filename;
-* it only outputs messages to users on standard error;
-* exits with code 0 unless an internal error occurred (or `--check` was
- used).
+_Black_ is a well-behaved Unix-style command-line tool:
+- it does nothing if no sources are passed to it;
+- it will read from standard input and write to standard output if `-` is used as the
+ filename;
+- it only outputs messages to users on standard error;
+- exits with code 0 unless an internal error occurred (or `--check` was used).
-### NOTE: This is a beta product
+### Using _Black_ with other tools
+
+While _Black_ enforces formatting that conforms to PEP 8, other tools may raise warnings
+about _Black_'s changes or will overwrite _Black_'s changes. A good example of this is
+[isort](https://pypi.org/p/isort). Since _Black_ is barely configurable, these tools
+should be configured to neither warn about nor overwrite _Black_'s changes.
+
+Actual details on _Black_ compatible configurations for various tools can be found in
+[compatible_configs](https://github.com/psf/black/blob/master/docs/compatible_configs.md).
+
+### Migrating your code style without ruining git blame
+
+A long-standing argument against moving to automated code formatters like _Black_ is
+that the migration will clutter up the output of `git blame`. This was a valid argument,
+but since Git version 2.23, Git natively supports
+[ignoring revisions in blame](https://git-scm.com/docs/git-blame#Documentation/git-blame.txt---ignore-revltrevgt)
+with the `--ignore-rev` option. You can also pass a file listing the revisions to ignore
+using the `--ignore-revs-file` option. The changes made by the revision will be ignored
+when assigning blame. Lines modified by an ignored revision will be blamed on the
+previous revision that modified those lines.
+
+So when migrating your project's code style to _Black_, reformat everything and commit
+the changes (preferably in one massive commit). Then put the full 40 characters commit
+identifier(s) into a file.
+
+```
+# Migrate code style to Black
+5b4ab991dede475d393e9d69ec388fd6bd949699
+```
+
+Afterwards, you can pass that file to `git blame` and see clean and meaningful blame
+information.
+
+```console
+$ git blame important.py --ignore-revs-file .git-blame-ignore-revs
+7a1ae265 (John Smith 2019-04-15 15:55:13 -0400 1) def very_important_function(text, file):
+abdfd8b0 (Alice Doe 2019-09-23 11:39:32 -0400 2) text = text.lstrip()
+7a1ae265 (John Smith 2019-04-15 15:55:13 -0400 3) with open(file, "r+") as f:
+7a1ae265 (John Smith 2019-04-15 15:55:13 -0400 4) f.write(formatted)
+```
-*Black* is already successfully used by several projects, small and big.
-It also sports a decent test suite. However, it is still very new.
-Things will probably be wonky for a while. This is made explicit by the
-"Beta" trove classifier, as well as by the "b" in the version number.
-What this means for you is that **until the formatter becomes stable,
-you should expect some formatting to change in the future**. That being
-said, no drastic stylistic changes are planned, mostly responses to bug
-reports.
+You can even configure `git` to automatically ignore revisions listed in a file on every
+call to `git blame`.
-Also, as a temporary safety measure, *Black* will check that the
-reformatted code still produces a valid AST that is equivalent to the
-original. This slows it down. If you're feeling confident, use
-``--fast``.
+```console
+$ git config blame.ignoreRevsFile .git-blame-ignore-revs
+```
+
+**The one caveat is that GitHub and GitLab do not yet support ignoring revisions using
+their native UI of blame.** So blame information will be cluttered with a reformatting
+commit on those platforms. (If you'd like this feature, there's an open issue for
+[GitLab](https://gitlab.com/gitlab-org/gitlab/-/issues/31423) and please let GitHub
+know!)
+
+### NOTE: This is a beta product
+
+_Black_ is already [successfully used](#used-by) by many projects, small and big. It
+also sports a decent test suite. However, it is still very new. Things will probably be
+wonky for a while. This is made explicit by the "Beta" trove classifier, as well as by
+the "b" in the version number. What this means for you is that **until the formatter
+becomes stable, you should expect some formatting to change in the future**. That being
+said, no drastic stylistic changes are planned, mostly responses to bug reports.
+Also, as a temporary safety measure, _Black_ will check that the reformatted code still
+produces a valid AST that is equivalent to the original. This slows it down. If you're
+feeling confident, use `--fast`.
-## The *Black* code style
+## The _Black_ code style
-*Black* reformats entire files in place. It is not configurable. It
-doesn't take previous formatting into account. It doesn't reformat
-blocks that start with `# fmt: off` and end with `# fmt: on`. `# fmt: on/off`
-have to be on the same level of indentation. It also
-recognizes [YAPF](https://github.com/google/yapf)'s block comments to
-the same effect, as a courtesy for straddling code.
+_Black_ reformats entire files in place. It is not configurable. It doesn't take
+previous formatting into account. It doesn't reformat blocks that start with
+`# fmt: off` and end with `# fmt: on`. `# fmt: on/off` have to be on the same level of
+indentation. It also recognizes [YAPF](https://github.com/google/yapf)'s block comments
+to the same effect, as a courtesy for straddling code.
+### How _Black_ wraps lines
-### How *Black* wraps lines
+_Black_ ignores previous formatting and applies uniform horizontal and vertical
+whitespace to your code. The rules for horizontal whitespace can be summarized as: do
+whatever makes `pycodestyle` happy. The coding style used by _Black_ can be viewed as a
+strict subset of PEP 8.
-*Black* ignores previous formatting and applies uniform horizontal
-and vertical whitespace to your code. The rules for horizontal
-whitespace can be summarized as: do whatever makes `pycodestyle` happy.
-The coding style used by *Black* can be viewed as a strict subset of
-PEP 8.
+As for vertical whitespace, _Black_ tries to render one full expression or simple
+statement per line. If this fits the allotted line length, great.
-As for vertical whitespace, *Black* tries to render one full expression
-or simple statement per line. If this fits the allotted line length,
-great.
```py3
# in:
-l = [1,
+j = [1,
2,
- 3,
+ 3
]
# out:
-l = [1, 2, 3]
+j = [1, 2, 3]
```
-If not, *Black* will look at the contents of the first outer matching
-brackets and put that in a separate indented line.
+If not, _Black_ will look at the contents of the first outer matching brackets and put
+that in a separate indented line.
+
```py3
# in:
-TracebackException.from_exception(exc, limit, lookup_lines, capture_locals)
+ImportantClass.important_method(exc, limit, lookup_lines, capture_locals, extra_argument)
# out:
-TracebackException.from_exception(
- exc, limit, lookup_lines, capture_locals
+ImportantClass.important_method(
+ exc, limit, lookup_lines, capture_locals, extra_argument
)
```
-If that still doesn't fit the bill, it will decompose the internal
-expression further using the same rule, indenting matching brackets
-every time. If the contents of the matching brackets pair are
-comma-separated (like an argument list, or a dict literal, and so on)
-then *Black* will first try to keep them on the same line with the
-matching brackets. If that doesn't work, it will put all of them in
-separate lines.
+If that still doesn't fit the bill, it will decompose the internal expression further
+using the same rule, indenting matching brackets every time. If the contents of the
+matching brackets pair are comma-separated (like an argument list, or a dict literal,
+and so on) then _Black_ will first try to keep them on the same line with the matching
+brackets. If that doesn't work, it will put all of them in separate lines.
+
```py3
# in:
-def very_important_function(template: str, *variables, file: os.PathLike, debug: bool = False):
+def very_important_function(template: str, *variables, file: os.PathLike, engine: str, header: bool = True, debug: bool = False):
"""Applies `variables` to the `template` and writes to `file`."""
with open(file, 'w') as f:
...
template: str,
*variables,
file: os.PathLike,
+ engine: str,
+ header: bool = True,
debug: bool = False,
):
"""Applies `variables` to the `template` and writes to `file`."""
...
```
-You might have noticed that closing brackets are always dedented and
-that a trailing comma is always added. Such formatting produces smaller
-diffs; when you add or remove an element, it's always just one line.
-Also, having the closing bracket dedented provides a clear delimiter
-between two distinct sections of the code that otherwise share the same
-indentation level (like the arguments list and the docstring in the
-example above).
-
-If a data structure literal (tuple, list, set, dict) or a line of "from"
-imports cannot fit in the allotted length, it's always split into one
-element per line. This minimizes diffs as well as enables readers of
-code to find which commit introduced a particular entry. This also
-makes *Black* compatible with [isort](https://pypi.org/p/isort/) with
+_Black_ prefers parentheses over backslashes, and will remove backslashes if found.
+
+```py3
+# in:
+
+if some_short_rule1 \
+ and some_short_rule2:
+ ...
+
+# out:
+
+if some_short_rule1 and some_short_rule2:
+ ...
+
+
+# in:
+
+if some_long_rule1 \
+ and some_long_rule2:
+ ...
+
+# out:
+
+if (
+ some_long_rule1
+ and some_long_rule2
+):
+ ...
+
+```
+
+Backslashes and multiline strings are one of the two places in the Python grammar that
+break significant indentation. You never need backslashes, they are used to force the
+grammar to accept breaks that would otherwise be parse errors. That makes them confusing
+to look at and brittle to modify. This is why _Black_ always gets rid of them.
+
+If you're reaching for backslashes, that's a clear signal that you can do better if you
+slightly refactor your code. I hope some of the examples above show you that there are
+many ways in which you can do it.
+
+However there is one exception: `with` statements using multiple context managers.
+Python's grammar does not allow organizing parentheses around the series of context
+managers.
+
+We don't want formatting like:
+
+```py3
+with make_context_manager1() as cm1, make_context_manager2() as cm2, make_context_manager3() as cm3, make_context_manager4() as cm4:
+ ... # nothing to split on - line too long
+```
+
+So _Black_ will now format it like this:
+
+```py3
+with \
+ make_context_manager(1) as cm1, \
+ make_context_manager(2) as cm2, \
+ make_context_manager(3) as cm3, \
+ make_context_manager(4) as cm4 \
+:
+ ... # backslashes and an ugly stranded colon
+```
+
+You might have noticed that closing brackets are always dedented and that a trailing
+comma is always added. Such formatting produces smaller diffs; when you add or remove an
+element, it's always just one line. Also, having the closing bracket dedented provides a
+clear delimiter between two distinct sections of the code that otherwise share the same
+indentation level (like the arguments list and the docstring in the example above).
+
+If a data structure literal (tuple, list, set, dict) or a line of "from" imports cannot
+fit in the allotted length, it's always split into one element per line. This minimizes
+diffs as well as enables readers of code to find which commit introduced a particular
+entry. This also makes _Black_ compatible with [isort](https://pypi.org/p/isort/) with
the following configuration.
<details>
```
The equivalent command line is:
+
```
$ isort --multi-line=3 --trailing-comma --force-grid-wrap=0 --use-parentheses --line-width=88 [ file.py ]
```
+
</details>
### Line length
-You probably noticed the peculiar default line length. *Black* defaults
-to 88 characters per line, which happens to be 10% over 80. This number
-was found to produce significantly shorter files than sticking with 80
-(the most popular), or even 79 (used by the standard library). In
-general, [90-ish seems like the wise choice](https://youtu.be/wf-BqAjZb8M?t=260).
-
-If you're paid by the line of code you write, you can pass
-`--line-length` with a lower number. *Black* will try to respect that.
-However, sometimes it won't be able to without breaking other rules. In
-those rare cases, auto-formatted code will exceed your allotted limit.
-
-You can also increase it, but remember that people with sight disabilities
-find it harder to work with line lengths exceeding 100 characters.
-It also adversely affects side-by-side diff review on typical screen
-resolutions. Long lines also make it harder to present code neatly
-in documentation or talk slides.
-
-If you're using Flake8, you can bump `max-line-length` to 88 and forget
-about it. Alternatively, use [Bugbear](https://github.com/PyCQA/flake8-bugbear)'s
-B950 warning instead of E501 and keep the max line length at 80 which
-you are probably already using. You'd do it like this:
+You probably noticed the peculiar default line length. _Black_ defaults to 88 characters
+per line, which happens to be 10% over 80. This number was found to produce
+significantly shorter files than sticking with 80 (the most popular), or even 79 (used
+by the standard library). In general,
+[90-ish seems like the wise choice](https://youtu.be/wf-BqAjZb8M?t=260).
+
+If you're paid by the line of code you write, you can pass `--line-length` with a lower
+number. _Black_ will try to respect that. However, sometimes it won't be able to without
+breaking other rules. In those rare cases, auto-formatted code will exceed your allotted
+limit.
+
+You can also increase it, but remember that people with sight disabilities find it
+harder to work with line lengths exceeding 100 characters. It also adversely affects
+side-by-side diff review on typical screen resolutions. Long lines also make it harder
+to present code neatly in documentation or talk slides.
+
+If you're using Flake8, you can bump `max-line-length` to 88 and forget about it.
+Alternatively, use [Bugbear](https://github.com/PyCQA/flake8-bugbear)'s B950 warning
+instead of E501 and keep the max line length at 80 which you are probably already using.
+You'd do it like this:
+
```ini
[flake8]
max-line-length = 80
...
select = C,E,F,W,B,B950
-ignore = E501
+ignore = E203, E501, W503
```
-You'll find *Black*'s own .flake8 config file is configured like this.
-If you're curious about the reasoning behind B950,
+You'll find _Black_'s own .flake8 config file is configured like this. Explanation of
+why W503 and E203 are disabled can be found further in this documentation. And if you're
+curious about the reasoning behind B950,
[Bugbear's documentation](https://github.com/PyCQA/flake8-bugbear#opinionated-warnings)
-explains it. The tl;dr is "it's like highway speed limits, we won't
-bother you if you overdo it by a few km/h".
+explains it. The tl;dr is "it's like highway speed limits, we won't bother you if you
+overdo it by a few km/h".
+
+**If you're looking for a minimal, black-compatible flake8 configuration:**
+```ini
+[flake8]
+max-line-length = 88
+extend-ignore = E203
+```
### Empty lines
-*Black* avoids spurious vertical whitespace. This is in the spirit of
-PEP 8 which says that in-function vertical whitespace should only be
-used sparingly.
+_Black_ avoids spurious vertical whitespace. This is in the spirit of PEP 8 which says
+that in-function vertical whitespace should only be used sparingly.
-*Black* will allow single empty lines inside functions, and single and
-double empty lines on module level left by the original editors, except
-when they're within parenthesized expressions. Since such expressions
-are always reformatted to fit minimal space, this whitespace is lost.
+_Black_ will allow single empty lines inside functions, and single and double empty
+lines on module level left by the original editors, except when they're within
+parenthesized expressions. Since such expressions are always reformatted to fit minimal
+space, this whitespace is lost.
-It will also insert proper spacing before and after function definitions.
-It's one line before and after inner functions and two lines before and
-after module-level functions and classes. *Black* will not put empty
-lines between function/class definitions and standalone comments that
-immediately precede the given function/class.
+It will also insert proper spacing before and after function definitions. It's one line
+before and after inner functions and two lines before and after module-level functions
+and classes. _Black_ will not put empty lines between function/class definitions and
+standalone comments that immediately precede the given function/class.
-*Black* will enforce single empty lines between a class-level docstring
-and the first following field or method. This conforms to
+_Black_ will enforce single empty lines between a class-level docstring and the first
+following field or method. This conforms to
[PEP 257](https://www.python.org/dev/peps/pep-0257/#multi-line-docstrings).
-*Black* won't insert empty lines after function docstrings unless that
-empty line is required due to an inner function starting immediately
-after.
-
+_Black_ won't insert empty lines after function docstrings unless that empty line is
+required due to an inner function starting immediately after.
### Trailing commas
-*Black* will add trailing commas to expressions that are split
-by comma where each element is on its own line. This includes function
-signatures.
-
-Unnecessary trailing commas are removed if an expression fits in one
-line. This makes it 1% more likely that your line won't exceed the
-allotted line length limit. Moreover, in this scenario, if you added
-another argument to your call, you'd probably fit it in the same line
-anyway. That doesn't make diffs any larger.
-
-One exception to removing trailing commas is tuple expressions with
-just one element. In this case *Black* won't touch the single trailing
-comma as this would unexpectedly change the underlying data type. Note
-that this is also the case when commas are used while indexing. This is
-a tuple in disguise: ```numpy_array[3, ]```.
-
-One exception to adding trailing commas is function signatures
-containing `*`, `*args`, or `**kwargs`. In this case a trailing comma
-is only safe to use on Python 3.6. *Black* will detect if your file is
-already 3.6+ only and use trailing commas in this situation. If you
-wonder how it knows, it looks for f-strings and existing use of trailing
-commas in function signatures that have stars in them. In other words,
-if you'd like a trailing comma in this situation and *Black* didn't
-recognize it was safe to do so, put it there manually and *Black* will
-keep it.
+_Black_ will add trailing commas to expressions that are split by comma where each
+element is on its own line. This includes function signatures.
+
+Unnecessary trailing commas are removed if an expression fits in one line. This makes it
+1% more likely that your line won't exceed the allotted line length limit. Moreover, in
+this scenario, if you added another argument to your call, you'd probably fit it in the
+same line anyway. That doesn't make diffs any larger.
+
+One exception to removing trailing commas is tuple expressions with just one element. In
+this case _Black_ won't touch the single trailing comma as this would unexpectedly
+change the underlying data type. Note that this is also the case when commas are used
+while indexing. This is a tuple in disguise: `numpy_array[3, ]`.
+One exception to adding trailing commas is function signatures containing `*`, `*args`,
+or `**kwargs`. In this case a trailing comma is only safe to use on Python 3.6. _Black_
+will detect if your file is already 3.6+ only and use trailing commas in this situation.
+If you wonder how it knows, it looks for f-strings and existing use of trailing commas
+in function signatures that have stars in them. In other words, if you'd like a trailing
+comma in this situation and _Black_ didn't recognize it was safe to do so, put it there
+manually and _Black_ will keep it.
### Strings
-*Black* prefers double quotes (`"` and `"""`) over single quotes (`'`
-and `'''`). It will replace the latter with the former as long as it
-does not result in more backslash escapes than before.
-
-*Black* also standardizes string prefixes, making them always lowercase.
-On top of that, if your code is already Python 3.6+ only or it's using
-the `unicode_literals` future import, *Black* will remove `u` from the
-string prefix as it is meaningless in those scenarios.
-
-The main reason to standardize on a single form of quotes is aesthetics.
-Having one kind of quotes everywhere reduces reader distraction.
-It will also enable a future version of *Black* to merge consecutive
-string literals that ended up on the same line (see
-[#26](https://github.com/ambv/black/issues/26) for details).
-
-Why settle on double quotes? They anticipate apostrophes in English
-text. They match the docstring standard described in [PEP 257](https://www.python.org/dev/peps/pep-0257/#what-is-a-docstring).
-An empty string in double quotes (`""`) is impossible to confuse with
-a one double-quote regardless of fonts and syntax highlighting used.
-On top of this, double quotes for strings are consistent with C which
-Python interacts a lot with.
-
-On certain keyboard layouts like US English, typing single quotes is
-a bit easier than double quotes. The latter requires use of the Shift
-key. My recommendation here is to keep using whatever is faster to type
-and let *Black* handle the transformation.
-
-If you are adopting *Black* in a large project with pre-existing string
-conventions (like the popular ["single quotes for data, double quotes for
-human-readable strings"](https://stackoverflow.com/a/56190)), you can
-pass `--skip-string-normalization` on the command line. This is meant as
-an adoption helper, avoid using this for new projects.
+_Black_ prefers double quotes (`"` and `"""`) over single quotes (`'` and `'''`). It
+will replace the latter with the former as long as it does not result in more backslash
+escapes than before.
+
+_Black_ also standardizes string prefixes, making them always lowercase. On top of that,
+if your code is already Python 3.6+ only or it's using the `unicode_literals` future
+import, _Black_ will remove `u` from the string prefix as it is meaningless in those
+scenarios.
+
+The main reason to standardize on a single form of quotes is aesthetics. Having one kind
+of quotes everywhere reduces reader distraction. It will also enable a future version of
+_Black_ to merge consecutive string literals that ended up on the same line (see
+[#26](https://github.com/psf/black/issues/26) for details).
+
+Why settle on double quotes? They anticipate apostrophes in English text. They match the
+docstring standard described in
+[PEP 257](https://www.python.org/dev/peps/pep-0257/#what-is-a-docstring). An empty
+string in double quotes (`""`) is impossible to confuse with a one double-quote
+regardless of fonts and syntax highlighting used. On top of this, double quotes for
+strings are consistent with C which Python interacts a lot with.
+
+On certain keyboard layouts like US English, typing single quotes is a bit easier than
+double quotes. The latter requires use of the Shift key. My recommendation here is to
+keep using whatever is faster to type and let _Black_ handle the transformation.
+
+If you are adopting _Black_ in a large project with pre-existing string conventions
+(like the popular
+["single quotes for data, double quotes for human-readable strings"](https://stackoverflow.com/a/56190)),
+you can pass `--skip-string-normalization` on the command line. This is meant as an
+adoption helper, avoid using this for new projects.
### Numeric literals
-*Black* standardizes most numeric literals to use lowercase letters for the
-syntactic parts and uppercase letters for the digits themselves: `0xAB`
-instead of `0XAB` and `1e10` instead of `1E10`. Python 2 long literals are
-styled as `2L` instead of `2l` to avoid confusion between `l` and `1`. In
-Python 3.6+, *Black* adds underscores to long numeric literals to aid
-readability: `100000000` becomes `100_000_000`.
-
-For regions where numerals are grouped differently (like [India](https://en.wikipedia.org/wiki/Indian_numbering_system)
-and [China](https://en.wikipedia.org/wiki/Chinese_numerals#Whole_numbers)),
-the `-N` or `--skip-numeric-underscore-normalization` command line option
-makes *Black* preserve underscores in numeric literals.
+_Black_ standardizes most numeric literals to use lowercase letters for the syntactic
+parts and uppercase letters for the digits themselves: `0xAB` instead of `0XAB` and
+`1e10` instead of `1E10`. Python 2 long literals are styled as `2L` instead of `2l` to
+avoid confusion between `l` and `1`.
### Line breaks & binary operators
-*Black* will break a line before a binary operator when splitting a block
-of code over multiple lines. This is so that *Black* is compliant with the
-recent changes in the [PEP 8](https://www.python.org/dev/peps/pep-0008/#should-a-line-break-before-or-after-a-binary-operator)
+_Black_ will break a line before a binary operator when splitting a block of code over
+multiple lines. This is so that _Black_ is compliant with the recent changes in the
+[PEP 8](https://www.python.org/dev/peps/pep-0008/#should-a-line-break-before-or-after-a-binary-operator)
style guide, which emphasizes that this approach improves readability.
-This behaviour may raise ``W503 line break before binary operator`` warnings in
-style guide enforcement tools like Flake8. Since ``W503`` is not PEP 8 compliant,
-you should tell Flake8 to ignore these warnings.
-
+This behaviour may raise `W503 line break before binary operator` warnings in style
+guide enforcement tools like Flake8. Since `W503` is not PEP 8 compliant, you should
+tell Flake8 to ignore these warnings.
### Slices
-PEP 8 [recommends](https://www.python.org/dev/peps/pep-0008/#whitespace-in-expressions-and-statements)
-to treat ``:`` in slices as a binary operator with the lowest priority, and to
-leave an equal amount of space on either side, except if a parameter is omitted
-(e.g. ``ham[1 + 1 :]``). It also states that for extended slices, both ``:``
-operators have to have the same amount of spacing, except if a parameter is
-omitted (``ham[1 + 1 ::]``). *Black* enforces these rules consistently.
-
-This behaviour may raise ``E203 whitespace before ':'`` warnings in style guide
-enforcement tools like Flake8. Since ``E203`` is not PEP 8 compliant, you should
-tell Flake8 to ignore these warnings.
-
+PEP 8
+[recommends](https://www.python.org/dev/peps/pep-0008/#whitespace-in-expressions-and-statements)
+to treat `:` in slices as a binary operator with the lowest priority, and to leave an
+equal amount of space on either side, except if a parameter is omitted (e.g.
+`ham[1 + 1 :]`). It recommends no spaces around `:` operators for "simple expressions"
+(`ham[lower:upper]`), and extra space for "complex expressions"
+(`ham[lower : upper + offset]`). _Black_ treats anything more than variable names as
+"complex" (`ham[lower : upper + 1]`). It also states that for extended slices, both `:`
+operators have to have the same amount of spacing, except if a parameter is omitted
+(`ham[1 + 1 ::]`). _Black_ enforces these rules consistently.
+
+This behaviour may raise `E203 whitespace before ':'` warnings in style guide
+enforcement tools like Flake8. Since `E203` is not PEP 8 compliant, you should tell
+Flake8 to ignore these warnings.
### Parentheses
-Some parentheses are optional in the Python grammar. Any expression can
-be wrapped in a pair of parentheses to form an atom. There are a few
-interesting cases:
+Some parentheses are optional in the Python grammar. Any expression can be wrapped in a
+pair of parentheses to form an atom. There are a few interesting cases:
- `if (...):`
- `while (...):`
- `some, *un, packing = (...)`
- `augmented += (...)`
-In those cases, parentheses are removed when the entire statement fits
-in one line, or if the inner expression doesn't have any delimiters to
-further split on. If there is only a single delimiter and the expression
-starts or ends with a bracket, the parenthesis can also be successfully
-omitted since the existing bracket pair will organize the expression
-neatly anyway. Otherwise, the parentheses are added.
-
-Please note that *Black* does not add or remove any additional nested
-parentheses that you might want to have for clarity or further
-code organization. For example those parentheses are not going to be
-removed:
+In those cases, parentheses are removed when the entire statement fits in one line, or
+if the inner expression doesn't have any delimiters to further split on. If there is
+only a single delimiter and the expression starts or ends with a bracket, the
+parenthesis can also be successfully omitted since the existing bracket pair will
+organize the expression neatly anyway. Otherwise, the parentheses are added.
+
+Please note that _Black_ does not add or remove any additional nested parentheses that
+you might want to have for clarity or further code organization. For example those
+parentheses are not going to be removed:
+
```py3
return not (this or that)
decision = (maybe.this() and values > 0) or (maybe.that() and values < 0)
```
-
### Call chains
-Some popular APIs, like ORMs, use call chaining. This API style is known
-as a [fluent interface](https://en.wikipedia.org/wiki/Fluent_interface).
-*Black* formats those by treating dots that follow a call or an indexing
-operation like a very low priority delimiter. It's easier to show the
-behavior than to explain it. Look at the example:
+Some popular APIs, like ORMs, use call chaining. This API style is known as a
+[fluent interface](https://en.wikipedia.org/wiki/Fluent_interface). _Black_ formats
+those by treating dots that follow a call or an indexing operation like a very low
+priority delimiter. It's easier to show the behavior than to explain it. Look at the
+example:
+
```py3
def example(session):
result = (
)
```
-
### Typing stub files
-PEP 484 describes the syntax for type hints in Python. One of the
-use cases for typing is providing type annotations for modules which
-cannot contain them directly (they might be written in C, or they might
-be third-party, or their implementation may be overly dynamic, and so on).
-
-To solve this, [stub files with the `.pyi` file
-extension](https://www.python.org/dev/peps/pep-0484/#stub-files) can be
-used to describe typing information for an external module. Those stub
-files omit the implementation of classes and functions they
-describe, instead they only contain the structure of the file (listing
-globals, functions, and classes with their members). The recommended
-code style for those files is more terse than PEP 8:
-
-* prefer `...` on the same line as the class/function signature;
-* avoid vertical whitespace between consecutive module-level functions,
- names, or methods and fields within a single class;
-* use a single blank line between top-level class definitions, or none
- if the classes are very small.
-
-*Black* enforces the above rules. There are additional guidelines for
-formatting `.pyi` file that are not enforced yet but might be in
-a future version of the formatter:
-
-* all function bodies should be empty (contain `...` instead of the body);
-* do not use docstrings;
-* prefer `...` over `pass`;
-* for arguments with a default, use `...` instead of the actual default;
-* avoid using string literals in type annotations, stub files support
- forward references natively (like Python 3.7 code with `from __future__
- import annotations`);
-* use variable annotations instead of type comments, even for stubs that
- target older versions of Python;
-* for arguments that default to `None`, use `Optional[]` explicitly;
-* use `float` instead of `Union[int, float]`.
+PEP 484 describes the syntax for type hints in Python. One of the use cases for typing
+is providing type annotations for modules which cannot contain them directly (they might
+be written in C, or they might be third-party, or their implementation may be overly
+dynamic, and so on).
+To solve this,
+[stub files with the `.pyi` file extension](https://www.python.org/dev/peps/pep-0484/#stub-files)
+can be used to describe typing information for an external module. Those stub files omit
+the implementation of classes and functions they describe, instead they only contain the
+structure of the file (listing globals, functions, and classes with their members). The
+recommended code style for those files is more terse than PEP 8:
-## pyproject.toml
+- prefer `...` on the same line as the class/function signature;
+- avoid vertical whitespace between consecutive module-level functions, names, or
+ methods and fields within a single class;
+- use a single blank line between top-level class definitions, or none if the classes
+ are very small.
-*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`
-patterns for your project.
+_Black_ enforces the above rules. There are additional guidelines for formatting `.pyi`
+file that are not enforced yet but might be in a future version of the formatter:
-**Pro-tip**: If you're asking yourself "Do I need to configure anything?"
-the answer is "No". *Black* is all about sensible defaults.
+- all function bodies should be empty (contain `...` instead of the body);
+- do not use docstrings;
+- prefer `...` over `pass`;
+- for arguments with a default, use `...` instead of the actual default;
+- avoid using string literals in type annotations, stub files support forward references
+ natively (like Python 3.7 code with `from __future__ import annotations`);
+- use variable annotations instead of type comments, even for stubs that target older
+ versions of Python;
+- for arguments that default to `None`, use `Optional[]` explicitly;
+- use `float` instead of `Union[int, float]`.
+## Pragmatism
-### What on Earth is a `pyproject.toml` file?
+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. This section documents
+what those exceptions are and why this is the case.
-[PEP 518](https://www.python.org/dev/peps/pep-0518/) defines
-`pyproject.toml` as a configuration file to store build system
-requirements for Python projects. With the help of tools
-like [Poetry](https://poetry.eustace.io/) or
-[Flit](https://flit.readthedocs.io/en/latest/) it can fully replace the
-need for `setup.py` and `setup.cfg` files.
+### The magic trailing comma
+_Black_ in general does not take existing formatting into account.
-### Where *Black* looks for the file
+However, there are cases where you put a short collection or function call in your code
+but you anticipate it will grow in the future.
-By default *Black* looks for `pyproject.toml` starting from the common
-base directory of all files and directories passed on the command line.
-If it's not there, it looks in parent directories. It stops looking
-when it finds the file, or a `.git` directory, or a `.hg` directory,
-or the root of the file system, whichever comes first.
+For example:
-If you're formatting standard input, *Black* will look for configuration
-starting from the current working directory.
+```py3
+TRANSLATIONS = {
+ "en_us": "English (US)",
+ "pl_pl": "polski",
+}
+```
-You can also explicitly specify the path to a particular file that you
-want with `--config`. In this situation *Black* will not look for any
-other file.
+Early versions of _Black_ used to ruthlessly collapse those into one line (it fits!).
+Now, you can communicate that you don't want that by putting a trailing comma in the
+collection yourself. When you do, _Black_ will know to always explode your collection
+into one item per line.
-If you're running with `--verbose`, you will see a blue message if
-a file was found and used.
+How do you make it stop? Just delete that trailing comma and _Black_ will collapse your
+collection into one line if it fits.
-Please note `blackd` will not use `pyproject.toml` configuration.
+### r"strings" and R"strings"
+
+_Black_ normalizes string quotes as well as string prefixes, making them lowercase. One
+exception to this rule is r-strings. It turns out that the very popular
+[MagicPython](https://github.com/MagicStack/MagicPython/) syntax highlighter, used by
+default by (among others) GitHub and Visual Studio Code, differentiates between
+r-strings and R-strings. The former are syntax highlighted as regular expressions while
+the latter are treated as true raw strings with no special semantics.
+
+## pyproject.toml
+
+_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` patterns for your project.
+**Pro-tip**: If you're asking yourself "Do I need to configure anything?" the answer is
+"No". _Black_ is all about sensible defaults.
+
+### What on Earth is a `pyproject.toml` file?
+
+[PEP 518](https://www.python.org/dev/peps/pep-0518/) defines `pyproject.toml` as a
+configuration file to store build system requirements for Python projects. With the help
+of tools like [Poetry](https://poetry.eustace.io/) or
+[Flit](https://flit.readthedocs.io/en/latest/) it can fully replace the need for
+`setup.py` and `setup.cfg` files.
+
+### Where _Black_ looks for the file
+
+By default _Black_ looks for `pyproject.toml` starting from the common base directory of
+all files and directories passed on the command line. If it's not there, it looks in
+parent directories. It stops looking when it finds the file, or a `.git` directory, or a
+`.hg` directory, or the root of the file system, whichever comes first.
+
+If you're formatting standard input, _Black_ will look for configuration starting from
+the current working directory.
+
+You can also explicitly specify the path to a particular file that you want with
+`--config`. In this situation _Black_ will not look for any other file.
+
+If you're running with `--verbose`, you will see a blue message if a file was found and
+used.
+
+Please note `blackd` will not use `pyproject.toml` configuration.
### Configuration format
-As the file extension suggests, `pyproject.toml` is a [TOML](https://github.com/toml-lang/toml) file. It contains separate
-sections for different tools. *Black* is using the `[tool.black]`
-section. The option keys are the same as long names of options on
-the command line.
+As the file extension suggests, `pyproject.toml` is a
+[TOML](https://github.com/toml-lang/toml) file. It contains separate sections for
+different tools. _Black_ is using the `[tool.black]` section. The option keys are the
+same as long names of options on the command line.
-Note that you have to use single-quoted strings in TOML for regular
-expressions. It's the equivalent of r-strings in Python. Multiline
-strings are treated as verbose regular expressions by Black. Use `[ ]`
-to denote a significant space character.
+Note that you have to use single-quoted strings in TOML for regular expressions. It's
+the equivalent of r-strings in Python. Multiline strings are treated as verbose regular
+expressions by Black. Use `[ ]` to denote a significant space character.
<details>
<summary>Example `pyproject.toml`</summary>
```toml
[tool.black]
line-length = 88
-py36 = true
+target-version = ['py37']
include = '\.pyi?$'
exclude = '''
### Lookup hierarchy
-Command-line options have defaults that you can see in `--help`.
-A `pyproject.toml` can override those defaults. Finally, options
-provided by the user on the command line override both.
-
-*Black* will only ever use one `pyproject.toml` file during an entire
-run. It doesn't look for multiple files, and doesn't compose
-configuration from different levels of the file hierarchy.
+Command-line options have defaults that you can see in `--help`. A `pyproject.toml` can
+override those defaults. Finally, options provided by the user on the command line
+override both.
+_Black_ will only ever use one `pyproject.toml` file during an entire run. It doesn't
+look for multiple files, and doesn't compose configuration from different levels of the
+file hierarchy.
## Editor integration
### Emacs
-Use [proofit404/blacken](https://github.com/proofit404/blacken).
+Options include the following:
+- [purcell/reformatter.el](https://github.com/purcell/reformatter.el)
+- [proofit404/blacken](https://github.com/proofit404/blacken)
+- [Elpy](https://github.com/jorgenschaefer/elpy).
-### PyCharm
+### PyCharm/IntelliJ IDEA
1. Install `black`.
2. Locate your `black` installation folder.
- On macOS / Linux / BSD:
+On macOS / Linux / BSD:
```console
$ which black
/usr/local/bin/black # possible location
```
- On Windows:
+On Windows:
```console
$ where black
%LocalAppData%\Programs\Python\Python36-32\Scripts\black.exe # possible location
```
-3. Open External tools in PyCharm with `File -> Settings -> Tools -> External Tools`.
+Note that if you are using a virtual environment detected by PyCharm, this is an
+unneeded step. In this case the path to `black` is `$PyInterpreterDirectory$/black`.
-4. Click the + icon to add a new external tool with the following values:
- - Name: Black
- - Description: Black is the uncompromising Python code formatter.
- - Program: <install_location_from_step_2>
- - Arguments: `$FilePath$`
+3. Open External tools in PyCharm/IntelliJ IDEA
-5. Format the currently opened file by selecting `Tools -> External Tools -> black`.
- - Alternatively, you can set a keyboard shortcut by navigating to `Preferences -> Keymap -> External Tools -> External Tools - Black`.
+On macOS:
-6. Optionally, run Black on every file save:
+`PyCharm -> Preferences -> Tools -> External Tools`
- 1. Make sure you have the [File Watcher](https://plugins.jetbrains.com/plugin/7177-file-watchers) plugin installed.
- 2. Go to `Preferences -> Tools -> File Watchers` and click `+` to add a new watcher:
- - Name: Black
- - File type: Python
- - Scope: Project Files
- - Program: <install_location_from_step_2>
- - Arguments: `$FilePath$`
- - Output paths to refresh: `$FilePathRelativeToProjectRoot$`
- - Working directory: `$ProjectFileDir$`
+On Windows / Linux / BSD:
-### Vim
+`File -> Settings -> Tools -> External Tools`
-Commands and shortcuts:
+4. Click the + icon to add a new external tool with the following values:
-* `:Black` to format the entire file (ranges not supported);
-* `:BlackUpgrade` to upgrade *Black* inside the virtualenv;
-* `:BlackVersion` to get the current version of *Black* inside the
- virtualenv.
+ - Name: Black
+ - Description: Black is the uncompromising Python code formatter.
+ - Program: <install_location_from_step_2>
+ - Arguments: `"$FilePath$"`
-Configuration:
-* `g:black_fast` (defaults to `0`)
-* `g:black_linelength` (defaults to `88`)
-* `g:black_skip_string_normalization` (defaults to `0`)
-* `g:black_virtualenv` (defaults to `~/.vim/black`)
+5. Format the currently opened file by selecting `Tools -> External Tools -> black`.
-To install with [vim-plug](https://github.com/junegunn/vim-plug):
+ - Alternatively, you can set a keyboard shortcut by navigating to
+ `Preferences or Settings -> Keymap -> External Tools -> External Tools - Black`.
-```
-Plug 'ambv/black'
-```
+6. Optionally, run _Black_ on every file save:
-or with [Vundle](https://github.com/VundleVim/Vundle.vim):
+ 1. Make sure you have the
+ [File Watchers](https://plugins.jetbrains.com/plugin/7177-file-watchers) plugin
+ installed.
+ 2. Go to `Preferences or Settings -> Tools -> File Watchers` and click `+` to add a
+ new watcher:
+ - Name: Black
+ - File type: Python
+ - Scope: Project Files
+ - Program: <install_location_from_step_2>
+ - Arguments: `$FilePath$`
+ - Output paths to refresh: `$FilePath$`
+ - Working directory: `$ProjectFileDir$`
-```
-Plugin 'ambv/black'
-```
+ - Uncheck "Auto-save edited files to trigger the watcher" in Advanced Options
-or you can copy the plugin from [plugin/black.vim](https://github.com/ambv/black/tree/master/plugin/black.vim).
-Let me know if this requires any changes to work with Vim 8's builtin
-`packadd`, or Pathogen, and so on.
+### Wing IDE
-This plugin **requires Vim 7.0+ built with Python 3.6+ support**. It
-needs Python 3.6 to be able to run *Black* inside the Vim process which
-is much faster than calling an external command.
+Wing supports black via the OS Commands tool, as explained in the Wing documentation on
+[pep8 formatting](https://wingware.com/doc/edit/pep8). The detailed procedure is:
-On first run, the plugin creates its own virtualenv using the right
-Python version and automatically installs *Black*. You can upgrade it later
-by calling `:BlackUpgrade` and restarting Vim.
-
-If you need to do anything special to make your virtualenv work and
-install *Black* (for example you want to run a version from master),
-create a virtualenv manually and point `g:black_virtualenv` to it.
-The plugin will use it.
-
-To run *Black* on save, add the following line to `.vimrc` or `init.vim`:
+1. Install `black`.
-```
-autocmd BufWritePre *.py execute ':Black'
+```console
+$ pip install black
```
-**How to get Vim with Python 3.6?**
-On Ubuntu 17.10 Vim comes with Python 3.6 by default.
-On macOS with Homebrew run: `brew install vim --with-python3`.
-When building Vim from source, use:
-`./configure --enable-python3interp=yes`. There's many guides online how
-to do this.
+2. Make sure it runs from the command line, e.g.
+```console
+$ black --help
+```
-### Visual Studio Code
+3. In Wing IDE, activate the **OS Commands** panel and define the command **black** to
+ execute black on the currently selected file:
-Use the [Python extension](https://marketplace.visualstudio.com/items?itemName=ms-python.python)
-([instructions](https://code.visualstudio.com/docs/python/editing#_formatting)).
+- Use the Tools -> OS Commands menu selection
+- click on **+** in **OS Commands** -> New: Command line..
+ - Title: black
+ - Command Line: black %s
+ - I/O Encoding: Use Default
+ - Key Binding: F1
+ - [x] Raise OS Commands when executed
+ - [x] Auto-save files before execution
+ - [x] Line mode
+4. Select a file in the editor and press **F1** , or whatever key binding you selected
+ in step 3, to reformat the file.
-### SublimeText 3
+### Vim
-Use [sublack plugin](https://github.com/jgirardet/sublack).
+Commands and shortcuts:
+- `:Black` to format the entire file (ranges not supported);
+- `:BlackUpgrade` to upgrade _Black_ inside the virtualenv;
+- `:BlackVersion` to get the current version of _Black_ inside the virtualenv.
-### Jupyter Notebook Magic
+Configuration:
-Use [blackcellmagic](https://github.com/csurfer/blackcellmagic).
+- `g:black_fast` (defaults to `0`)
+- `g:black_linelength` (defaults to `88`)
+- `g:black_skip_string_normalization` (defaults to `0`)
+- `g:black_virtualenv` (defaults to `~/.vim/black` or `~/.local/share/nvim/black`)
+To install with [vim-plug](https://github.com/junegunn/vim-plug):
-### Python Language Server
+```
+Plug 'psf/black', { 'branch': 'stable' }
+```
-If your editor supports the [Language Server Protocol](https://langserver.org/)
-(Atom, Sublime Text, Visual Studio Code and many more), you can use
-the [Python Language Server](https://github.com/palantir/python-language-server) with the
-[pyls-black](https://github.com/rupert/pyls-black) plugin.
+or with [Vundle](https://github.com/VundleVim/Vundle.vim):
+```
+Plugin 'psf/black'
+```
-### Atom/Nuclide
+and execute the following in a terminal:
-Use [python-black](https://atom.io/packages/python-black).
+```console
+$ cd ~/.vim/bundle/black
+$ git checkout origin/stable -b stable
+```
+or you can copy the plugin from
+[plugin/black.vim](https://github.com/psf/black/blob/stable/plugin/black.vim).
-### Other editors
+```
+mkdir -p ~/.vim/pack/python/start/black/plugin
+curl https://raw.githubusercontent.com/psf/black/master/plugin/black.vim -o ~/.vim/pack/python/start/black/plugin/black.vim
+```
-Other editors will require external contributions.
+Let me know if this requires any changes to work with Vim 8's builtin `packadd`, or
+Pathogen, and so on.
-Patches welcome! ✨ 🍰 ✨
+This plugin **requires Vim 7.0+ built with Python 3.6+ support**. It needs Python 3.6 to
+be able to run _Black_ inside the Vim process which is much faster than calling an
+external command.
-Any tool that can pipe code through *Black* using its stdio mode (just
-[use `-` as the file name](https://www.tldp.org/LDP/abs/html/special-chars.html#DASHREF2)).
-The formatted code will be returned on stdout (unless `--check` was
-passed). *Black* will still emit messages on stderr but that shouldn't
-affect your use case.
+On first run, the plugin creates its own virtualenv using the right Python version and
+automatically installs _Black_. You can upgrade it later by calling `:BlackUpgrade` and
+restarting Vim.
-This can be used for example with PyCharm's [File Watchers](https://www.jetbrains.com/help/pycharm/file-watchers.html).
+If you need to do anything special to make your virtualenv work and install _Black_ (for
+example you want to run a version from master), create a virtualenv manually and point
+`g:black_virtualenv` to it. The plugin will use it.
-## blackd
+To run _Black_ on save, add the following line to `.vimrc` or `init.vim`:
-`blackd` is a small HTTP server that exposes *Black*'s functionality over
-a simple protocol. The main benefit of using it is to avoid paying the
-cost of starting up a new *Black* process every time you want to blacken
-a file.
+```
+autocmd BufWritePre *.py execute ':Black'
+```
-### Usage
+To run _Black_ on a key press (e.g. F9 below), add this:
-`blackd` is not packaged alongside *Black* by default because it has additional
-dependencies. You will need to do `pip install black[d]` to install it.
+```
+nnoremap <F9> :Black<CR>
+```
-You can start the server on the default port, binding only to the local interface
-by running `blackd`. You will see a single line mentioning the server's version,
-and the host and port it's listening on. `blackd` will then print an access log
-similar to most web servers on standard output, merged with any exception traces
-caused by invalid formatting requests.
+**How to get Vim with Python 3.6?** On Ubuntu 17.10 Vim comes with Python 3.6 by
+default. On macOS with Homebrew run: `brew install vim`. When building Vim from source,
+use: `./configure --enable-python3interp=yes`. There's many guides online how to do
+this.
-`blackd` provides even less options than *Black*. You can see them by running
-`blackd --help`:
+**I get an import error when using _Black_ from a virtual environment**: If you get an
+error message like this:
```text
-Usage: blackd [OPTIONS]
-
-Options:
- --bind-host TEXT Address to bind the server to.
- --bind-port INTEGER Port to listen on
- --version Show the version and exit.
- -h, --help Show this message and exit.
+Traceback (most recent call last):
+ File "<string>", line 63, in <module>
+ File "/home/gui/.vim/black/lib/python3.7/site-packages/black.py", line 45, in <module>
+ from typed_ast import ast3, ast27
+ File "/home/gui/.vim/black/lib/python3.7/site-packages/typed_ast/ast3.py", line 40, in <module>
+ from typed_ast import _ast3
+ImportError: /home/gui/.vim/black/lib/python3.7/site-packages/typed_ast/_ast3.cpython-37m-x86_64-linux-gnu.so: undefined symbool: PyExc_KeyboardInterrupt
```
-### Protocol
-
-`blackd` only accepts `POST` requests at the `/` path. The body of the request
-should contain the python source code to be formatted, encoded
-according to the `charset` field in the `Content-Type` request header. If no
-`charset` is specified, `blackd` assumes `UTF-8`.
-
-There are a few HTTP headers that control how the source is formatted. These
-correspond to command line flags for *Black*. There is one exception to this:
-`X-Protocol-Version` which if present, should have the value `1`, otherwise the
-request is rejected with `HTTP 501` (Not Implemented).
-
-The headers controlling how code is formatted are:
+Then you need to install `typed_ast` and `regex` directly from the source code. The
+error happens because `pip` will download [Python wheels](https://pythonwheels.com/) if
+they are available. Python wheels are a new standard of distributing Python packages and
+packages that have Cython and extensions written in C are already compiled, so the
+installation is much more faster. The problem here is that somehow the Python
+environment inside Vim does not match with those already compiled C extensions and these
+kind of errors are the result. Luckily there is an easy fix: installing the packages
+from the source code.
- - `X-Line-Length`: corresponds to the `--line-length` command line flag.
- - `X-Skip-String-Normalization`: corresponds to the `--skip-string-normalization`
- command line flag. If present and its value is not the empty string, no string
- normalization will be performed.
- - `X-Skip-Numeric-Underscore-Normalization`: corresponds to the
- `--skip-numeric-underscore-normalization` command line flag.
- - `X-Fast-Or-Safe`: if set to `fast`, `blackd` will act as *Black* does when
- passed the `--fast` command line flag.
- - `X-Python-Variant`: if set to `pyi`, `blackd` will act as *Black* does when
- passed the `--pyi` command line flag. Otherwise, its value must correspond to
- a Python version. If this value represents at least Python 3.6, `blackd` will
- act as *Black* does when passed the `--py36` command line flag.
-
-If any of these headers are set to invalid values, `blackd` returns a `HTTP 400`
-error response, mentioning the name of the problematic header in the message body.
+The two packages that cause the problem are:
-Apart from the above, `blackd` can produce the following response codes:
+- [regex](https://pypi.org/project/regex/)
+- [typed-ast](https://pypi.org/project/typed-ast/)
- - `HTTP 204`: If the input is already well-formatted. The response body is
- empty.
- - `HTTP 200`: If formatting was needed on the input. The response body
- contains the blackened Python code, and the `Content-Type` header is set
- accordingly.
- - `HTTP 400`: If the input contains a syntax error. Details of the error are
- returned in the response body.
- - `HTTP 500`: If there was any kind of error while trying to format the input.
- The response body contains a textual representation of the error.
+Now remove those two packages:
-## Version control integration
-
-Use [pre-commit](https://pre-commit.com/). Once you [have it
-installed](https://pre-commit.com/#install), add this to the
-`.pre-commit-config.yaml` in your repository:
-```yaml
-repos:
-- repo: https://github.com/ambv/black
- rev: stable
- hooks:
- - id: black
- language_version: python3.6
+```console
+$ pip uninstall regex typed-ast -y
```
-Then run `pre-commit install` and you're ready to go.
-
-Avoid using `args` in the hook. Instead, store necessary configuration
-in `pyproject.toml` so that editors and command-line usage of Black all
-behave consistently for your project. See *Black*'s own `pyproject.toml`
-for an example.
-If you're already using Python 3.7, switch the `language_version`
-accordingly. Finally, `stable` is a tag that is pinned to the latest
-release on PyPI. If you'd rather run on master, this is also an option.
+And now you can install them with:
+```console
+$ pip install --no-binary :all: regex typed-ast
+```
-## Ignoring unmodified files
-
-*Black* remembers files it has already formatted, unless the `--diff` flag is used or
-code is passed via standard input. This information is stored per-user. The exact
-location of the file depends on the *Black* version and the system on which *Black*
-is run. The file is non-portable. The standard location on common operating systems
-is:
-
-* Windows: `C:\\Users\<username>\AppData\Local\black\black\Cache\<version>\cache.<line-length>.<file-mode>.pickle`
-* macOS: `/Users/<username>/Library/Caches/black/<version>/cache.<line-length>.<file-mode>.pickle`
-* Linux: `/home/<username>/.cache/black/<version>/cache.<line-length>.<file-mode>.pickle`
-
-`file-mode` is an int flag that determines whether the file was formatted as 3.6+ only,
-as .pyi, and whether string normalization was omitted.
+The C extensions will be compiled and now Vim's Python environment will match. Note that
+you need to have the GCC compiler and the Python development files installed (on
+Ubuntu/Debian do `sudo apt-get install build-essential python3-dev`).
+If you later want to update _Black_, you should do it like this:
-## Testimonials
+```console
+$ pip install -U black --no-binary regex,typed-ast
+```
-**Dusty Phillips**, [writer](https://smile.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=dusty+phillips):
+### Visual Studio Code
-> *Black* is opinionated so you don't have to be.
+Use the
+[Python extension](https://marketplace.visualstudio.com/items?itemName=ms-python.python)
+([instructions](https://code.visualstudio.com/docs/python/editing#_formatting)).
-**Hynek Schlawack**, [creator of `attrs`](https://www.attrs.org/), core
-developer of Twisted and CPython:
+### SublimeText 3
-> An auto-formatter that doesn't suck is all I want for Xmas!
+Use [sublack plugin](https://github.com/jgirardet/sublack).
-**Carl Meyer**, [Django](https://www.djangoproject.com/) core developer:
+### Jupyter Notebook Magic
-> At least the name is good.
+Use [blackcellmagic](https://github.com/csurfer/blackcellmagic).
-**Kenneth Reitz**, creator of [`requests`](http://python-requests.org/)
-and [`pipenv`](https://docs.pipenv.org/):
+### Python Language Server
-> This vastly improves the formatting of our code. Thanks a ton!
+If your editor supports the [Language Server Protocol](https://langserver.org/) (Atom,
+Sublime Text, Visual Studio Code and many more), you can use the
+[Python Language Server](https://github.com/palantir/python-language-server) with the
+[pyls-black](https://github.com/rupert/pyls-black) plugin.
+### Atom/Nuclide
-## Show your style
+Use [python-black](https://atom.io/packages/python-black).
-Use the badge in your project's README.md:
+### Kakoune
-```markdown
-[](https://github.com/ambv/black)
-```
+Add the following hook to your kakrc, then run _Black_ with `:format`.
-Using the badge in README.rst:
```
-.. image:: https://img.shields.io/badge/code%20style-black-000000.svg
- :target: https://github.com/ambv/black
+hook global WinSetOption filetype=python %{
+ set-option window formatcmd 'black -q -'
+}
```
-Looks like this: [](https://github.com/ambv/black)
-
-
-## License
-
-MIT
-
-
-## Contributing to *Black*
-
-In terms of inspiration, *Black* is about as configurable as *gofmt*.
-This is deliberate.
-
-Bug reports and fixes are always welcome! However, before you suggest a
-new feature or configuration knob, ask yourself why you want it. If it
-enables better integration with some workflow, fixes an inconsistency,
-speeds things up, and so on - go for it! On the other hand, if your
-answer is "because I don't like a particular formatting" then you're not
-ready to embrace *Black* yet. Such changes are unlikely to get accepted.
-You can still try but prepare to be disappointed.
-
-More details can be found in [CONTRIBUTING](CONTRIBUTING.md).
-
-
-## Change Log
-
-### 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](#blackd) 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](http://mpastell.com/pweave/) and
- [Spyder IDE](https://pythonhosted.org/spyder/) 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)
+### Thonny
-* added `--verbose` (#283)
+Use [Thonny-black-code-format](https://github.com/Franccisco/thonny-black-code-format).
-* 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](https://en.wikipedia.org/wiki/Fluent_interface)
- 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
+### Other editors
-* don't populate the cache on `--check` (#175)
+Other editors will require external contributions.
+Patches welcome! ✨ 🍰 ✨
-### 18.4a3
+Any tool that can pipe code through _Black_ using its stdio mode (just
+[use `-` as the file name](https://www.tldp.org/LDP/abs/html/special-chars.html#DASHREF2)).
+The formatted code will be returned on stdout (unless `--check` was passed). _Black_
+will still emit messages on stderr but that shouldn't affect your use case.
-* added a "cache"; files already reformatted that haven't changed on disk
- won't be reformatted again (#109)
+This can be used for example with PyCharm's or IntelliJ's
+[File Watchers](https://www.jetbrains.com/help/pycharm/file-watchers.html).
-* `--check` and `--diff` are no longer mutually exclusive (#149)
+## blackd
-* generalized star expression handling, including double stars; this
- fixes multiplication making expressions "unsafe" for trailing commas (#132)
+`blackd` is a small HTTP server that exposes _Black_'s functionality over a simple
+protocol. The main benefit of using it is to avoid paying the cost of starting up a new
+_Black_ process every time you want to blacken a file.
-* *Black* no longer enforces putting empty lines behind control flow statements
- (#90)
+### Usage
-* *Black* now splits imports like "Mode 3 + trailing comma" of isort (#127)
+`blackd` is not packaged alongside _Black_ by default because it has additional
+dependencies. You will need to do `pip install black[d]` to install it.
-* fixed comment indentation when a standalone comment closes a block (#16, #32)
+You can start the server on the default port, binding only to the local interface by
+running `blackd`. You will see a single line mentioning the server's version, and the
+host and port it's listening on. `blackd` will then print an access log similar to most
+web servers on standard output, merged with any exception traces caused by invalid
+formatting requests.
-* fixed standalone comments receiving extra empty lines if immediately preceding
- a class, def, or decorator (#56, #154)
+`blackd` provides even less options than _Black_. You can see them by running
+`blackd --help`:
-* fixed `--diff` not showing entire path (#130)
+```text
+Usage: blackd [OPTIONS]
-* fixed parsing of complex expressions after star and double stars in
- function calls (#2)
+Options:
+ --bind-host TEXT Address to bind the server to.
+ --bind-port INTEGER Port to listen on
+ --version Show the version and exit.
+ -h, --help Show this message and exit.
+```
-* fixed invalid splitting on comma in lambda arguments (#133)
+There is no official blackd client tool (yet!). You can test that blackd is working
+using `curl`:
-* fixed missing splits of ternary expressions (#141)
+```sh
+blackd --bind-port 9090 & # or let blackd choose a port
+curl -s -XPOST "localhost:9090" -d "print('valid')"
+```
+### Protocol
-### 18.4a2
+`blackd` only accepts `POST` requests at the `/` path. The body of the request should
+contain the python source code to be formatted, encoded according to the `charset` field
+in the `Content-Type` request header. If no `charset` is specified, `blackd` assumes
+`UTF-8`.
-* fixed parsing of unaligned standalone comments (#99, #112)
+There are a few HTTP headers that control how the source is formatted. These correspond
+to command line flags for _Black_. There is one exception to this: `X-Protocol-Version`
+which if present, should have the value `1`, otherwise the request is rejected with
+`HTTP 501` (Not Implemented).
-* fixed placement of dictionary unpacking inside dictionary literals (#111)
+The headers controlling how code is formatted are:
-* Vim plugin now works on Windows, too
+- `X-Line-Length`: corresponds to the `--line-length` command line flag.
+- `X-Skip-String-Normalization`: corresponds to the `--skip-string-normalization`
+ command line flag. If present and its value is not the empty string, no string
+ normalization will be performed.
+- `X-Fast-Or-Safe`: if set to `fast`, `blackd` will act as _Black_ does when passed the
+ `--fast` command line flag.
+- `X-Python-Variant`: if set to `pyi`, `blackd` will act as _Black_ does when passed the
+ `--pyi` command line flag. Otherwise, its value must correspond to a Python version or
+ a set of comma-separated Python versions, optionally prefixed with `py`. For example,
+ to request code that is compatible with Python 3.5 and 3.6, set the header to
+ `py3.5,py3.6`.
+- `X-Diff`: corresponds to the `--diff` command line flag. If present, a diff of the
+ formats will be output.
+
+If any of these headers are set to invalid values, `blackd` returns a `HTTP 400` error
+response, mentioning the name of the problematic header in the message body.
-* fixed unstable formatting when encountering unnecessarily escaped quotes
- in a string (#120)
+Apart from the above, `blackd` can produce the following response codes:
+- `HTTP 204`: If the input is already well-formatted. The response body is empty.
+- `HTTP 200`: If formatting was needed on the input. The response body contains the
+ blackened Python code, and the `Content-Type` header is set accordingly.
+- `HTTP 400`: If the input contains a syntax error. Details of the error are returned in
+ the response body.
+- `HTTP 500`: If there was any kind of error while trying to format the input. The
+ response body contains a textual representation of the error.
-### 18.4a1
+The response headers include a `X-Black-Version` header containing the version of
+_Black_.
-* added `--quiet` (#78)
+## black-primer
-* added automatic parentheses management (#4)
+`black-primer` is a tool built for CI (and huumans) to have _Black_ `--check` a number
+of (configured in `primer.json`) Git accessible projects in parallel. _(A PR will be
+accepted to add Mercurial support.)_
-* added [pre-commit](https://pre-commit.com) integration (#103, #104)
+### Run flow
-* fixed reporting on `--check` with multiple files (#101, #102)
+- Ensure we have a `black` + `git` in PATH
+- Load projects from `primer.json`
+- Run projects in parallel with `--worker` workers (defaults to CPU count / 2)
+ - Checkout projects
+ - Run black and record result
+ - Clean up repository checkout _(can optionally be disabled via `--keep`)_
+- Display results summary to screen
+- Default to cleaning up `--work-dir` (which defaults to tempfile schemantics)
+- Return
+ - 0 for successful run
+ - < 0 for environment / internal error
+ - > 0 for each project with an error
-* fixed removing backslash escapes from raw strings (#100, #105)
+### Speed up Runs 🏎
+If you're running locally yourself to test black on lots of code try:
-### 18.4a0
+- Using `-k` / `--keep` + `-w` / `--work-dir` so you don't have to re-checkout the repo
+ each run
-* added `--diff` (#87)
+### CLI Arguments
-* add line breaks before all delimiters, except in cases like commas, to
- better comply with PEP 8 (#73)
+```text
+Usage: black-primer [OPTIONS]
-* standardize string literals to use double quotes (almost) everywhere
- (#75)
+ primer - prime projects for blackening... 🏴
-* 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)
+Options:
+ -c, --config PATH JSON config file path [default: /Users/cooper/repos/
+ black/src/black_primer/primer.json]
-* fixed 18.3a4 regression: don't crash and burn on empty lines with
- trailing whitespace (#80)
+ --debug Turn on debug logging [default: False]
+ -k, --keep Keep workdir + repos post run [default: False]
+ -L, --long-checkouts Pull big projects to test [default: False]
+ -R, --rebase Rebase project if already checked out [default:
+ False]
-* fixed 18.3a4 regression: `# yapf: disable` usage as trailing comment
- would cause *Black* to not emit the rest of the file (#95)
+ -w, --workdir PATH Directory Path for repo checkouts [default: /var/fol
+ ders/tc/hbwxh76j1hn6gqjd2n2sjn4j9k1glp/T/primer.20200
+ 517125229]
-* when CTRL+C is pressed while formatting many files, *Black* no longer
- freaks out with a flurry of asyncio-related exceptions
+ -W, --workers INTEGER Number of parallel worker coroutines [default: 69]
+ -h, --help Show this message and exit.
+```
-* only allow up to two empty lines on module level and only single empty
- lines within functions (#74)
+### primer config file
+
+The config is JSON format. Its main element is the `"projects"` dictionary. Below
+explains each parameter:
+
+```json
+{
+ "projects": {
+ "00_Example": {
+ "cli_arguments": "List of extra CLI arguments to pass Black for this project",
+ "expect_formatting_changes": "Boolean to indicate that the version of Black is expected to cause changes",
+ "git_clone_url": "URL you would pass `git clone` to check out this repo",
+ "long_checkout": "Boolean to have repo skipped by defauult unless `--long-checkouts` is specified",
+ "py_versions": "List of major Python versions to run this project with - all will do as you'd expect - run on ALL versions"
+ },
+ "aioexabgp": {
+ "cli_arguments": [],
+ "expect_formatting_changes": true,
+ "git_clone_url": "https://github.com/cooperlees/aioexabgp.git",
+ "long_checkout": false,
+ "py_versions": ["all", "3.8"] // "all" ignores all other versions
+ }
+ }
+}
+```
+### Example run
-### 18.3a4
+```console
+cooper-mbp:black cooper$ ~/venvs/b/bin/black-primer
+[2020-05-17 13:06:40,830] INFO: 4 projects to run Black over (lib.py:270)
+[2020-05-17 13:06:44,215] INFO: Analyzing results (lib.py:285)
+-- primer results 📊 --
+
+3 / 4 succeeded (75.0%) ✅
+1 / 4 FAILED (25.0%) 💩
+ - 0 projects disabled by config
+ - 0 projects skipped due to Python version
+ - 0 skipped due to long checkout
+
+Failed projects:
+
+## flake8-bugbear:
+ - Returned 1
+ - stdout:
+--- tests/b303_b304.py 2020-05-17 20:04:09.991227 +0000
++++ tests/b303_b304.py 2020-05-17 20:06:42.753851 +0000
+@@ -26,11 +26,11 @@
+ maxint = 5 # this is okay
+ # the following shouldn't crash
+ (a, b, c) = list(range(3))
+ # it's different than this
+ a, b, c = list(range(3))
+- a, b, c, = list(range(3))
++ a, b, c = list(range(3))
+ # and different than this
+ (a, b), c = list(range(3))
+ a, *b, c = [1, 2, 3, 4, 5]
+ b[1:3] = [0, 0]
+
+would reformat tests/b303_b304.py
+Oh no! 💥 💔 💥
+1 file would be reformatted, 22 files would be left unchanged.
+```
-* `# fmt: off` and `# fmt: on` are implemented (#5)
+## Version control integration
-* automatic detection of deprecated Python 2 forms of print statements
- and exec statements in the formatted file (#49)
+Use [pre-commit](https://pre-commit.com/). Once you
+[have it installed](https://pre-commit.com/#install), add this to the
+`.pre-commit-config.yaml` in your repository:
-* use proper spaces for complex expressions in default values of typed
- function arguments (#60)
+```yaml
+repos:
+ - repo: https://github.com/psf/black
+ rev: stable
+ hooks:
+ - id: black
+ language_version: python3.6
+```
-* only return exit code 1 when --check is used (#50)
+Then run `pre-commit install` and you're ready to go.
-* don't remove single trailing commas from square bracket indexing
- (#59)
+Avoid using `args` in the hook. Instead, store necessary configuration in
+`pyproject.toml` so that editors and command-line usage of Black all behave consistently
+for your project. See _Black_'s own
+[pyproject.toml](https://github.com/psf/black/blob/master/pyproject.toml) for an
+example.
-* don't omit whitespace if the previous factor leaf wasn't a math
- operator (#55)
+If you're already using Python 3.7, switch the `language_version` accordingly. Finally,
+`stable` is a branch that tracks the latest release on PyPI. If you'd rather run on
+master, this is also an option.
-* omit extra space in kwarg unpacking if it's the first argument (#46)
+## Ignoring unmodified files
-* omit extra space in [Sphinx auto-attribute comments](http://www.sphinx-doc.org/en/stable/ext/autodoc.html#directive-autoattribute)
- (#68)
+_Black_ remembers files it has already formatted, unless the `--diff` flag is used or
+code is passed via standard input. This information is stored per-user. The exact
+location of the file depends on the _Black_ version and the system on which _Black_ is
+run. The file is non-portable. The standard location on common operating systems is:
+- Windows:
+ `C:\\Users\<username>\AppData\Local\black\black\Cache\<version>\cache.<line-length>.<file-mode>.pickle`
+- macOS:
+ `/Users/<username>/Library/Caches/black/<version>/cache.<line-length>.<file-mode>.pickle`
+- Linux:
+ `/home/<username>/.cache/black/<version>/cache.<line-length>.<file-mode>.pickle`
-### 18.3a3
+`file-mode` is an int flag that determines whether the file was formatted as 3.6+ only,
+as .pyi, and whether string normalization was omitted.
-* don't remove single empty lines outside of bracketed expressions
- (#19)
+To override the location of these files on macOS or Linux, set the environment variable
+`XDG_CACHE_HOME` to your preferred location. For example, if you want to put the cache
+in the directory you're running _Black_ from, set `XDG_CACHE_HOME=.cache`. _Black_ will
+then write the above files to `.cache/black/<version>/`.
-* added ability to pipe formatting from stdin to stdin (#25)
+## Used by
-* restored ability to format code with legacy usage of `async` as
- a name (#20, #42)
+The following notable open-source projects trust _Black_ with enforcing a consistent
+code style: pytest, tox, Pyramid, Django Channels, Hypothesis, attrs, SQLAlchemy,
+Poetry, PyPA applications (Warehouse, Bandersnatch, Pipenv, virtualenv), pandas, Pillow,
+every Datadog Agent Integration, Home Assistant.
-* even better handling of numpy-style array indexing (#33, again)
+The following organizations use _Black_: Facebook, Dropbox.
+Are we missing anyone? Let us know.
-### 18.3a2
+## Testimonials
-* changed positioning of binary operators to occur at beginning of lines
- instead of at the end, following [a recent change to PEP 8](https://github.com/python/peps/commit/c59c4376ad233a62ca4b3a6060c81368bd21e85b)
- (#21)
+**Dusty Phillips**,
+[writer](https://smile.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=dusty+phillips):
-* ignore empty bracket pairs while splitting. This avoids very weirdly
- looking formattings (#34, #35)
+> _Black_ is opinionated so you don't have to be.
-* remove a trailing comma if there is a single argument to a call
+**Hynek Schlawack**, [creator of `attrs`](https://www.attrs.org/), core developer of
+Twisted and CPython:
-* if top level functions were separated by a comment, don't put four
- empty lines after the upper function
+> An auto-formatter that doesn't suck is all I want for Xmas!
-* fixed unstable formatting of newlines with imports
+**Carl Meyer**, [Django](https://www.djangoproject.com/) core developer:
-* fixed unintentional folding of post scriptum standalone comments
- into last statement if it was a simple statement (#18, #28)
+> At least the name is good.
-* fixed missing space in numpy-style array indexing (#33)
+**Kenneth Reitz**, creator of [`requests`](http://python-requests.org/) and
+[`pipenv`](https://docs.pipenv.org/):
-* fixed spurious space after star-based unary expressions (#31)
+> This vastly improves the formatting of our code. Thanks a ton!
+## Show your style
-### 18.3a1
+Use the badge in your project's README.md:
-* added `--check`
+```markdown
+[](https://github.com/psf/black)
+```
-* 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)
+Using the badge in README.rst:
-* fixed invalid spacing of dots in relative imports (#6, #13)
+```
+.. image:: https://img.shields.io/badge/code%20style-black-000000.svg
+ :target: https://github.com/psf/black
+```
-* fixed invalid splitting after comma on unpacked variables in for-loops
- (#23)
+Looks like this:
+[](https://github.com/psf/black)
-* fixed spurious space in parenthesized set expressions (#7)
+## License
-* fixed spurious space after opening parentheses and in default
- arguments (#14, #17)
+MIT
-* fixed spurious space after unary operators when the operand was
- a complex expression (#15)
+## Contributing to _Black_
+In terms of inspiration, _Black_ is about as configurable as _gofmt_. This is
+deliberate.
-### 18.3a0
+Bug reports and fixes are always welcome! However, before you suggest a new feature or
+configuration knob, ask yourself why you want it. If it enables better integration with
+some workflow, fixes an inconsistency, speeds things up, and so on - go for it! On the
+other hand, if your answer is "because I don't like a particular formatting" then you're
+not ready to embrace _Black_ yet. Such changes are unlikely to get accepted. You can
+still try but prepare to be disappointed.
-* first published version, Happy 🍰 Day 2018!
+More details can be found in
+[CONTRIBUTING](https://github.com/psf/black/blob/master/CONTRIBUTING.md).
-* alpha quality
+## Change Log
-* date-versioned (see: https://calver.org/)
+The log's become rather long. It moved to its own file.
+See [CHANGES](https://github.com/psf/black/blob/master/CHANGES.md).
## Authors
Maintained with [Carol Willing](mailto:carolcode@willingconsulting.com),
[Carl Meyer](mailto:carl@oddbird.net),
[Jelle Zijlstra](mailto:jelle.zijlstra@gmail.com),
-[Mika Naylor](mailto:mail@autophagy.io), and
-[Zsolt Dollenstein](mailto:zsol.zsol@gmail.com).
+[Mika Naylor](mailto:mail@autophagy.io),
+[Zsolt Dollenstein](mailto:zsol.zsol@gmail.com), and
+[Cooper Lees](mailto:me@cooperlees.com).
Multiple contributions by:
-* [Anthony Sottile](mailto:asottile@umich.edu)
-* [Artem Malyshev](mailto:proofit404@gmail.com)
-* [Christian Heimes](mailto:christian@python.org)
-* [Daniel M. Capella](mailto:polycitizen@gmail.com)
-* [Eli Treuherz](mailto:eli@treuherz.com)
-* Hugo van Kemenade
-* [Ivan Katanić](mailto:ivan.katanic@gmail.com)
-* [Jonas Obrist](mailto:ojiidotch@gmail.com)
-* [Luka Sterbic](mailto:luka.sterbic@gmail.com)
-* [Miguel Gaiowski](mailto:miggaiowski@gmail.com)
-* [Miroslav Shubernetskiy](mailto:miroslav@miki725.com)
-* [Neraste](mailto:neraste.herr10@gmail.com)
-* [Osaetin Daniel](mailto:osaetindaniel@gmail.com)
-* [Peter Bengtsson](mailto:mail@peterbe.com)
-* [Stavros Korokithakis](mailto:hi@stavros.io)
-* [Sunil Kapil](mailto:snlkapil@gmail.com)
-* [Vishwas B Sharma](mailto:sharma.vishwas88@gmail.com)
-* [Chuck Wooters](mailto:chuck.wooters@microsoft.com)
+
+- [Abdur-Rahmaan Janhangeer](mailto:arj.python@gmail.com)
+- [Adam Johnson](mailto:me@adamj.eu)
+- [Alexander Huynh](mailto:github@grande.coffee)
+- [Andrew Thorp](mailto:andrew.thorp.dev@gmail.com)
+- [Andrey](mailto:dyuuus@yandex.ru)
+- [Andy Freeland](mailto:andy@andyfreeland.net)
+- [Anthony Sottile](mailto:asottile@umich.edu)
+- [Arjaan Buijk](mailto:arjaan.buijk@gmail.com)
+- [Artem Malyshev](mailto:proofit404@gmail.com)
+- [Asger Hautop Drewsen](mailto:asgerdrewsen@gmail.com)
+- [Augie Fackler](mailto:raf@durin42.com)
+- [Aviskar KC](mailto:aviskarkc10@gmail.com)
+- [Benjamin Woodruff](mailto:github@benjam.info)
+- [Brandt Bucher](mailto:brandtbucher@gmail.com)
+- Charles Reid
+- [Christian Heimes](mailto:christian@python.org)
+- [Chuck Wooters](mailto:chuck.wooters@microsoft.com)
+- [Cooper Ry Lees](mailto:me@cooperlees.com)
+- [Daniel Hahler](mailto:github@thequod.de)
+- [Daniel M. Capella](mailto:polycitizen@gmail.com)
+- Daniele Esposti
+- dylanjblack
+- [Eli Treuherz](mailto:eli@treuherz.com)
+- [Florent Thiery](mailto:fthiery@gmail.com)
+- hauntsaninja
+- Hugo van Kemenade
+- [Ivan Katanić](mailto:ivan.katanic@gmail.com)
+- [Jason Fried](mailto:me@jasonfried.info)
+- [jgirardet](mailto:ijkl@netc.fr)
+- [Joe Antonakakis](mailto:jma353@cornell.edu)
+- [Jon Dufresne](mailto:jon.dufresne@gmail.com)
+- [Jonas Obrist](mailto:ojiidotch@gmail.com)
+- [Josh Bode](mailto:joshbode@fastmail.com)
+- [Juan Luis Cano Rodríguez](mailto:hello@juanlu.space)
+- [Katie McLaughlin](mailto:katie@glasnt.com)
+- Lawrence Chan
+- [Linus Groh](mailto:mail@linusgroh.de)
+- [Luka Sterbic](mailto:luka.sterbic@gmail.com)
+- Mariatta
+- [Matt VanEseltine](mailto:vaneseltine@gmail.com)
+- [Michael Flaxman](mailto:michael.flaxman@gmail.com)
+- [Michael J. Sullivan](mailto:sully@msully.net)
+- [Michael McClimon](mailto:michael@mcclimon.org)
+- [Miguel Gaiowski](mailto:miggaiowski@gmail.com)
+- [Mike](mailto:roshi@fedoraproject.org)
+- [Min ho Kim](mailto:minho42@gmail.com)
+- [Miroslav Shubernetskiy](mailto:miroslav@miki725.com)
+- [Neraste](mailto:neraste.herr10@gmail.com)
+- [Ofek Lev](mailto:ofekmeister@gmail.com)
+- [Osaetin Daniel](mailto:osaetindaniel@gmail.com)
+- [Pablo Galindo](mailto:Pablogsal@gmail.com)
+- [Peter Bengtsson](mailto:mail@peterbe.com)
+- pmacosta
+- [Rishikesh Jha](mailto:rishijha424@gmail.com)
+- [Stavros Korokithakis](mailto:hi@stavros.io)
+- [Stephen Rosen](mailto:sirosen@globus.org)
+- [Sunil Kapil](mailto:snlkapil@gmail.com)
+- [Thom Lu](mailto:thomas.c.lu@gmail.com)
+- [Tom Christie](mailto:tom@tomchristie.com)
+- [Tzu-ping Chung](mailto:uranusjr@gmail.com)
+- [Utsav Shah](mailto:ukshah2@illinois.edu)
+- vezeli
+- [Vishwas B Sharma](mailto:sharma.vishwas88@gmail.com)
+- [Yngve Høiseth](mailto:yngve@hoiseth.net)
+- [Yurii Karabas](mailto:1998uriyyo@gmail.com)
projects / etc / vim.git / blobdiff