X-Git-Url: https://git.madduck.net/etc/vim.git/blobdiff_plain/450983e33309cdd8b6ad3849ee86e8b5b3903706..8e38b6626be681adbb367820ce65e05254664629:/README.md?ds=inline diff --git a/README.md b/README.md index 3becfd3..def311f 100644 --- a/README.md +++ b/README.md @@ -1,45 +1,42 @@ -![Black Logo](https://raw.githubusercontent.com/ambv/black/master/docs/_static/logo2-readme.png) +![Black Logo](https://raw.githubusercontent.com/psf/black/master/docs/_static/logo2-readme.png) +

The Uncompromising Code Formatter

-Build Status +Build Status +Actions Status Documentation Status -Coverage Status -License: MIT -PyPI -Code style: black +Coverage Status +License: MIT +PyPI +Downloads +Code style: black

> “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)** | -**[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)** | +_Contents:_ **[Installation and usage](#installation-and-usage)** | +**[Code style](#the-black-code-style)** | **[Pragmatism](#pragmatism)** | +**[pyproject.toml](#pyprojecttoml)** | **[Editor integration](#editor-integration)** | +**[blackd](#blackd)** | **[Version control integration](#version-control-integration)** +| **[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)** --- @@ -48,9 +45,8 @@ Try it out now using the [Black Playground](https://black.now.sh). ### 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 @@ -62,137 +58,148 @@ 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]... 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. - --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?$] - --exclude TEXT A regular expression that matches files and - directories that should be excluded on - recursive searches. On Windows, use forward - slashes for directories. [default: - build/|buck-out/|dist/|_build/|\.git/|\.hg/| - \.mypy_cache/|\.tox/|\.venv/] - -q, --quiet Don't emit non-error messages to stderr. Errors - are still emitted, silence those with - 2>/dev/null. - -v, --verbose Also emit messages to stderr about files - that were not changed or were ignored due to - --exclude=. - --version Show the version and exit. - --config PATH Read configuration from PATH. - --help Show this message and exit. + Don't normalize string quotes or prefixes. + --check Don't write the files back, just return the + status. Return code 0 means nothing would + change. Return code 1 means some files + would be reformatted. Return code 123 means + there was an internal error. + --diff Don't write the files back, just output a + diff for each file on stdout. + --fast / --safe If --fast given, skip temporary sanity + checks. [default: --safe] + --include TEXT A regular expression that matches files and + directories that should be included on + recursive searches. An empty value means + all files are included regardless of the + name. Use forward slashes for directories + on all platforms (Windows, too). Exclusions + are calculated first, inclusions later. + [default: \.pyi?$] + --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|_build|buck- + out|build|dist)/] + -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. + -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 -*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. +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. -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``. +Actual details on _Black_ compatible configurations for various tools can be found in +[compatible_configs](./docs/compatible_configs.md). +### NOTE: This is a beta product -## The *Black* code style +_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. -*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`. It also -recognizes [YAPF](https://github.com/google/yapf)'s block comments to -the same effect, as a courtesy for straddling code. +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 -### How *Black* wraps lines +_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* 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. +### 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. + +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: ... @@ -203,6 +210,8 @@ 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`.""" @@ -210,19 +219,16 @@ def very_important_function( ... ``` -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 +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.
@@ -233,175 +239,178 @@ the following configuration. multi_line_output=3 include_trailing_comma=True force_grid_wrap=0 -combine_as_imports=True +use_parentheses=True line_length=88 ``` The equivalent command line is: + ``` -$ isort --multi-line=3 --trailing-comma --force-grid-wrap=0 --combine-as --line-width=88 [ file.py ] +$ isort --multi-line=3 --trailing-comma --force-grid-wrap=0 --use-parentheses --line-width=88 [ file.py ] ``` +
### 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, Bugbear's documentation -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". +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". +**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_ 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. +_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). +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. 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. +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. +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. +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`. ### 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 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 (...):` @@ -414,30 +423,29 @@ interesting cases: - `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 = ( @@ -451,96 +459,126 @@ def example(session): ) ``` - ### 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", +} +``` + +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. + +How do you make it stop? Just delete that trailing comma and _Black_ will collapse your +collection into one line if it fits. + +### 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. -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. +**Pro-tip**: If you're asking yourself "Do I need to configure anything?" the answer is +"No". _Black_ is all about sensible defaults. -If you're running with `--verbose`, you will see a blue message if -a file was found and used. +### 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.
Example `pyproject.toml` @@ -548,24 +586,26 @@ to denote a significant space character. ```toml [tool.black] line-length = 88 -py36 = true +target-version = ['py37'] include = '\.pyi?$' exclude = ''' -/( - \.git - | \.hg - | \.mypy_cache - | \.tox - | \.venv - | _build - | buck-out - | build - | dist - - # The following are specific to Black, you probably don't want those. - | blib2to3 - | tests/data -)/ + +( + /( + \.eggs # exclude a few common directories in the + | \.git # root of the project + | \.hg + | \.mypy_cache + | \.tox + | \.venv + | _build + | buck-out + | build + | dist + )/ + | foo.py # also separately exclude a file named foo.py in + # the root of the project +) ''' ``` @@ -573,23 +613,22 @@ 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). - +Use [proofit404/blacken](https://github.com/proofit404/blacken) or +[Elpy](https://github.com/jorgenschaefer/elpy). -### PyCharm +### PyCharm/IntelliJ IDEA 1. Install `black`. @@ -599,129 +638,207 @@ $ pip 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`. + +3. Open External tools in PyCharm/IntelliJ IDEA + +On macOS: + +`PyCharm -> Preferences -> Tools -> External Tools` + +On Windows / Linux / BSD: + +`File -> Settings -> Tools -> External Tools` 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: - - Arguments: `$FilePath$` + + - Name: Black + - Description: Black is the uncompromising Python code formatter. + - Program: + - Arguments: `"$FilePath$"` 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`. -6. Optionally, run Black on every file save: + - Alternatively, you can set a keyboard shortcut by navigating to + `Preferences or Settings -> Keymap -> External Tools -> External Tools - Black`. + +6. Optionally, run _Black_ on every file save: + + 1. Make sure you have the + [File Watcher](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: + - Arguments: `$FilePath$` + - Output paths to refresh: `$FilePath$` + - Working directory: `$ProjectFileDir$` + + - Uncheck "Auto-save edited files to trigger the watcher" + +### Wing IDE + +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: + +1. Install `black`. + +```console +$ pip install black +``` + +2. Make sure it runs from the command line, e.g. - 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: - - Arguments: `$FilePath$` - - Output paths to refresh: `$FilePathRelativeToProjectRoot$` - - Working directory: `$ProjectFileDir$` +```console +$ black --help +``` + +3. In Wing IDE, activate the **OS Commands** panel and define the command **black** to + execute black on the currently selected file: + +- 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. ### Vim Commands and shortcuts: -* `,=` or `: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. +- `: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. 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`) + +- `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): ``` -Plug 'ambv/black', +Plug 'psf/black', { 'branch': 'stable' } ``` or with [Vundle](https://github.com/VundleVim/Vundle.vim): ``` -Plugin 'ambv/black' +Plugin 'psf/black' ``` -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. +and execute the following in a terminal: -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. +```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). -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. +``` +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 +``` -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. +Let me know if this requires any changes to work with Vim 8's builtin `packadd`, or +Pathogen, and so on. -To run *Black* on save, add the following line to `.vimrc` or `init.vim`: +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. + +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`: ``` autocmd BufWritePre *.py execute ':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. +To run _Black_ on a key press (e.g. F9 below), add this: +``` +nnoremap :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`. When building Vim from source, +use: `./configure --enable-python3interp=yes`. There's many guides online how to do +this. ### Visual Studio Code -Use the [Python extension](https://marketplace.visualstudio.com/items?itemName=ms-python.python) +Use the +[Python extension](https://marketplace.visualstudio.com/items?itemName=ms-python.python) ([instructions](https://code.visualstudio.com/docs/python/editing#_formatting)). - ### SublimeText 3 Use [sublack plugin](https://github.com/jgirardet/sublack). - -### IPython Notebook Magic +### Jupyter Notebook Magic Use [blackcellmagic](https://github.com/csurfer/blackcellmagic). - ### Python Language Server -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 +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 -Use [atom-black](https://github.com/hauntsaninja/atom-black). +Use [python-black](https://atom.io/packages/python-black). + +### Kakoune +Add the following hook to your kakrc, then run black with `:format`. + +``` +hook global WinSetOption filetype=python %{ + set-option window formatcmd 'black -q -' +} +``` + +### Thonny + +Use [Thonny-black-code-format](https://github.com/Franccisco/thonny-black-code-format). ### Other editors @@ -729,61 +846,165 @@ Other editors will require external contributions. Patches welcome! ✨ 🍰 ✨ -Any tool that can pipe code through *Black* using its stdio mode (just +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. +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. + +This can be used for example with PyCharm's or IntelliJ's +[File Watchers](https://www.jetbrains.com/help/pycharm/file-watchers.html). + +## blackd + +`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. + +### Usage -This can be used for example with PyCharm's [File Watchers](https://www.jetbrains.com/help/pycharm/file-watchers.html). +`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. +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. + +`blackd` provides even less options than _Black_. You can see them by running +`blackd --help`: + +```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. +``` + +There is no official blackd client tool (yet!). You can test that blackd is working +using `curl`: + +``` +blackd --bind-port 9090 & # or let blackd choose a port +curl -s -XPOST "localhost:9090" -d "print('valid')" +``` + +### 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: + +- `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. + +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. + +The response headers include a `X-Black-Version` header containing the version of +_Black_. ## Version control integration -Use [pre-commit](https://pre-commit.com/). Once you [have it -installed](https://pre-commit.com/#install), add this to the +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 + - repo: https://github.com/psf/black rev: stable hooks: - - id: black - language_version: python3.6 + - id: black + language_version: python3.6 ``` -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. +Then run `pre-commit install` and you're ready to go. -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. +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. +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. ## Ignoring unmodified files -*Black* remembers files it has already formatted, unless the `--diff` flag is used or +_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: +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\\AppData\Local\black\black\Cache\\cache...pickle` +- macOS: + `/Users//Library/Caches/black//cache...pickle` +- Linux: + `/home//.cache/black//cache...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. + +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//`. + +## Used by -* Windows: `C:\\Users\\AppData\Local\black\black\Cache\\cache..pickle` -* macOS: `/Users//Library/Caches/black//cache..pickle` -* Linux: `/home//.cache/black//cache..pickle` +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, Pipenv, virtualenv), pandas, Pillow, every Datadog +Agent Integration, Home Assistant. +The following organizations use _Black_: Dropbox. + +Are we missing anyone? Let us know. ## Testimonials -**Dusty Phillips**, [writer](https://smile.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=dusty+phillips): +**Dusty Phillips**, +[writer](https://smile.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=dusty+phillips): -> *Black* is opinionated so you don't have to be. +> _Black_ is opinionated so you don't have to be. -**Hynek Schlawack**, [creator of `attrs`](http://www.attrs.org/), core -developer of Twisted and CPython: +**Hynek Schlawack**, [creator of `attrs`](https://www.attrs.org/), core developer of +Twisted and CPython: > An auto-formatter that doesn't suck is all I want for Xmas! @@ -791,402 +1012,52 @@ developer of Twisted and CPython: > At least the name is good. -**Kenneth Reitz**, creator of [`requests`](http://python-requests.org/) -and [`pipenv`](https://docs.pipenv.org/): +**Kenneth Reitz**, creator of [`requests`](http://python-requests.org/) and +[`pipenv`](https://docs.pipenv.org/): > This vastly improves the formatting of our code. Thanks a ton! - ## Show your style Use the badge in your project's README.md: ```markdown -[![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/ambv/black) +[![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black) ``` Using the badge in README.rst: + ``` .. image:: https://img.shields.io/badge/code%20style-black-000000.svg - :target: https://github.com/ambv/black + :target: https://github.com/psf/black ``` -Looks like this: [![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/ambv/black) - +Looks like this: +[![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black) ## License MIT +## Contributing to _Black_ -## Contributing to *Black* - -In terms of inspiration, *Black* is about as configurable as *gofmt*. -This is deliberate. +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. +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 -### 18.8b0 - -* fix parsing of `__future__` imports with renames (#389) -* fix scope of `# fmt: off` when directly preceding `yield` and other nodes (#385) - -### 18.6b4 - -* hotfix: don't freeze when multiple comments directly precede `# fmt: off` (#371) - - -### 18.6b3 - -* typing stub files (`.pyi`) now have blank lines added after constants (#340) - -* `# fmt: off` and `# fmt: on` are now much more dependable: - - * they now work also within bracket pairs (#329) - - * they now correctly work across function/class boundaries (#335) - - * they now work when an indentation block starts with empty lines or misaligned - comments (#334) - -* made Click not fail on invalid environments; note that Click is right but the - likelihood we'll need to access non-ASCII file paths when dealing with Python source - code is low (#277) - -* fixed improper formatting of f-strings with quotes inside interpolated - expressions (#322) - -* fixed unnecessary slowdown when long list literals where found in a file - -* fixed unnecessary slowdown on AST nodes with very many siblings - -* fixed cannibalizing backslashes during string normalization - -* fixed a crash due to symbolic links pointing outside of the project directory (#338) - - -### 18.6b2 - -* added `--config` (#65) - -* added `-h` equivalent to `--help` (#316) - -* fixed improper unmodified file caching when `-S` was used - -* fixed extra space in string unpacking (#305) - -* fixed formatting of empty triple quoted strings (#313) - -* fixed unnecessary slowdown in comment placement calculation on lines without - comments - - -### 18.6b1 - -* hotfix: don't output human-facing information on stdout (#299) - -* hotfix: don't output cake emoji on non-zero return code (#300) - - -### 18.6b0 - -* added `--include` and `--exclude` (#270) - -* added `--skip-string-normalization` (#118) - -* added `--verbose` (#283) - -* the header output in `--diff` now actually conforms to the unified diff spec - -* fixed long trivial assignments being wrapped in unnecessary parentheses (#273) - -* fixed unnecessary parentheses when a line contained multiline strings (#232) - -* fixed stdin handling not working correctly if an old version of Click was - used (#276) - -* *Black* now preserves line endings when formatting a file in place (#258) - - -### 18.5b1 - -* added `--pyi` (#249) - -* added `--py36` (#249) - -* Python grammar pickle caches are stored with the formatting caches, making - *Black* work in environments where site-packages is not user-writable (#192) - -* *Black* now enforces a PEP 257 empty line after a class-level docstring - (and/or fields) and the first method - -* fixed invalid code produced when standalone comments were present in a trailer - that was omitted from line splitting on a large expression (#237) - -* fixed optional parentheses being removed within `# fmt: off` sections (#224) - -* fixed invalid code produced when stars in very long imports were incorrectly - wrapped in optional parentheses (#234) - -* fixed unstable formatting when inline comments were moved around in - a trailer that was omitted from line splitting on a large expression - (#238) - -* fixed extra empty line between a class declaration and the first - method if no class docstring or fields are present (#219) - -* fixed extra empty line between a function signature and an inner - function or inner class (#196) - - -### 18.5b0 - -* call chains are now formatted according to the - [fluent interfaces](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 - -* don't populate the cache on `--check` (#175) - - -### 18.4a3 - -* added a "cache"; files already reformatted that haven't changed on disk - won't be reformatted again (#109) - -* `--check` and `--diff` are no longer mutually exclusive (#149) - -* generalized star expression handling, including double stars; this - fixes multiplication making expressions "unsafe" for trailing commas (#132) - -* *Black* no longer enforces putting empty lines behind control flow statements - (#90) - -* *Black* now splits imports like "Mode 3 + trailing comma" of isort (#127) - -* fixed comment indentation when a standalone comment closes a block (#16, #32) - -* fixed standalone comments receiving extra empty lines if immediately preceding - a class, def, or decorator (#56, #154) - -* fixed `--diff` not showing entire path (#130) - -* fixed parsing of complex expressions after star and double stars in - function calls (#2) - -* fixed invalid splitting on comma in lambda arguments (#133) - -* fixed missing splits of ternary expressions (#141) - - -### 18.4a2 - -* fixed parsing of unaligned standalone comments (#99, #112) - -* fixed placement of dictionary unpacking inside dictionary literals (#111) - -* Vim plugin now works on Windows, too - -* fixed unstable formatting when encountering unnecessarily escaped quotes - in a string (#120) - - -### 18.4a1 - -* added `--quiet` (#78) - -* added automatic parentheses management (#4) - -* added [pre-commit](https://pre-commit.com) integration (#103, #104) - -* fixed reporting on `--check` with multiple files (#101, #102) - -* fixed removing backslash escapes from raw strings (#100, #105) - - -### 18.4a0 - -* added `--diff` (#87) - -* add line breaks before all delimiters, except in cases like commas, to - better comply with PEP 8 (#73) - -* standardize string literals to use double quotes (almost) everywhere - (#75) - -* fixed handling of standalone comments within nested bracketed - expressions; *Black* will no longer produce super long lines or put all - standalone comments at the end of the expression (#22) - -* fixed 18.3a4 regression: don't crash and burn on empty lines with - trailing whitespace (#80) - -* fixed 18.3a4 regression: `# yapf: disable` usage as trailing comment - would cause *Black* to not emit the rest of the file (#95) - -* when CTRL+C is pressed while formatting many files, *Black* no longer - freaks out with a flurry of asyncio-related exceptions - -* only allow up to two empty lines on module level and only single empty - lines within functions (#74) - - -### 18.3a4 - -* `# fmt: off` and `# fmt: on` are implemented (#5) - -* automatic detection of deprecated Python 2 forms of print statements - and exec statements in the formatted file (#49) - -* use proper spaces for complex expressions in default values of typed - function arguments (#60) - -* only return exit code 1 when --check is used (#50) - -* don't remove single trailing commas from square bracket indexing - (#59) - -* don't omit whitespace if the previous factor leaf wasn't a math - operator (#55) - -* omit extra space in kwarg unpacking if it's the first argument (#46) - -* omit extra space in [Sphinx auto-attribute comments](http://www.sphinx-doc.org/en/stable/ext/autodoc.html#directive-autoattribute) - (#68) - - -### 18.3a3 - -* don't remove single empty lines outside of bracketed expressions - (#19) - -* added ability to pipe formatting from stdin to stdin (#25) - -* restored ability to format code with legacy usage of `async` as - a name (#20, #42) - -* even better handling of numpy-style array indexing (#33, again) - - -### 18.3a2 - -* changed positioning of binary operators to occur at beginning of lines - instead of at the end, following [a recent change to PEP 8](https://github.com/python/peps/commit/c59c4376ad233a62ca4b3a6060c81368bd21e85b) - (#21) - -* ignore empty bracket pairs while splitting. This avoids very weirdly - looking formattings (#34, #35) - -* remove a trailing comma if there is a single argument to a call - -* if top level functions were separated by a comment, don't put four - empty lines after the upper function - -* fixed unstable formatting of newlines with imports - -* fixed unintentional folding of post scriptum standalone comments - into last statement if it was a simple statement (#18, #28) - -* fixed missing space in numpy-style array indexing (#33) - -* fixed spurious space after star-based unary expressions (#31) - - -### 18.3a1 - -* added `--check` - -* only put trailing commas in function signatures and calls if it's - safe to do so. If the file is Python 3.6+ it's always safe, otherwise - only safe if there are no `*args` or `**kwargs` used in the signature - or call. (#8) - -* fixed invalid spacing of dots in relative imports (#6, #13) - -* fixed invalid splitting after comma on unpacked variables in for-loops - (#23) - -* fixed spurious space in parenthesized set expressions (#7) - -* fixed spurious space after opening parentheses and in default - arguments (#14, #17) - -* fixed spurious space after unary operators when the operand was - a complex expression (#15) - - -### 18.3a0 - -* first published version, Happy 🍰 Day 2018! - -* alpha quality - -* date-versioned (see: https://calver.org/) +The log's become rather long. It moved to its own file. +See [CHANGES](CHANGES.md). ## Authors @@ -1194,24 +1065,75 @@ Glued together by [Łukasz Langa](mailto:lukasz@langa.pl). Maintained with [Carol Willing](mailto:carolcode@willingconsulting.com), [Carl Meyer](mailto:carl@oddbird.net), -[Mika Naylor](mailto:mail@autophagy.io), and -[Zsolt Dollenstein](mailto:zsol.zsol@gmail.com). +[Jelle Zijlstra](mailto:jelle.zijlstra@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@cgi.com) -* Hugo van Kemenade -* [Ivan Katanić](mailto:ivan.katanic@gmail.com) -* [Jelle Zijlstra](mailto:jelle.zijlstra@gmail.com) -* [Jonas Obrist](mailto:ojiidotch@gmail.com) -* [Luka Sterbic](mailto:luka.sterbic@gmail.com) -* [Miguel Gaiowski](mailto:miggaiowski@gmail.com) -* [Neraste](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) + +- [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)