X-Git-Url: https://git.madduck.net/etc/vim.git/blobdiff_plain/4c480bcac288883040e6fda3c75825a0da54eb66..f3bb22a828495c66d8d2dae1edf45e15fc2daddb:/README.md?ds=sidebyside diff --git a/README.md b/README.md index ebff26a..dc93b37 100644 --- a/README.md +++ b/README.md @@ -1,12 +1,21 @@ -# black +![Black Logo](https://raw.githubusercontent.com/python/black/master/docs/_static/logo2-readme.png) +

The Uncompromising Code Formatter

-[![Build Status](https://travis-ci.org/ambv/black.svg?branch=master)](https://travis-ci.org/ambv/black) +

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

-> Any color you like. +> “Any color you like.” *Black* is the uncompromising Python code formatter. By using it, you -agree to cease control over minutiae of hand-formatting. In return, +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. @@ -18,70 +27,164 @@ content instead. *Black* makes code review faster by producing the smallest diffs possible. +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. -## NOTE: This is an early pre-release +--- -*Black* can already successfully format itself and the standard library. -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 -"Alpha" trove classifier, as well as by the "a" 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**. +*Contents:* **[Installation and usage](#installation-and-usage)** | +**[Code style](#the-black-code-style)** | +**[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)** -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``. +--- + +## Installation and usage + +### 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. -## Usage -*Black* can be installed by running `pip install black`. +### Usage +To get started right away with sensible defaults: + +``` +black {source_file_or_directory} ``` + +### Command line options + +*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] - --check Don't write back the files, just return the - status. Return code 0 means nothing changed. - Return code 1 means some files were reformatted. - Return code 123 means there was an internal - error. - --fast / --safe If --fast given, skip temporary sanity checks. - [default: --safe] - --version Show the version and exit. - --help Show this message and exit. + -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] + --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. Deprecated; use + --target-version instead. [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. 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). + + +### 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 philosophy behind *Black* +## 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`. It also +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* formats files +### How *Black* wraps lines *Black* ignores previous formatting and applies uniform horizontal and vertical whitespace to your code. The rules for horizontal -whitespace are pretty obvious and can be summarized as: do whatever -makes `pycodestyle` happy. +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. ```py3 # in: + l = [1, 2, 3, ] # out: + l = [1, 2, 3] ``` @@ -89,12 +192,14 @@ If not, *Black* will look at the contents of the first outer matching brackets and put that in a separate indented line. ```py3 # in: -l = [[n for n in list_bosses()], [n for n in list_employees()]] + +ImportantClass.important_method(exc, limit, lookup_lines, capture_locals, extra_argument) # out: -l = [ - [n for n in list_bosses()], [n for n in list_employees()] -] + +ImportantClass.important_method( + exc, limit, lookup_lines, capture_locals, extra_argument +) ``` If that still doesn't fit the bill, it will decompose the internal @@ -106,21 +211,24 @@ 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: ... # out: + 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: + with open(file, "w") as f: ... ``` @@ -132,20 +240,30 @@ 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). -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. +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. -*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. One exception is control flow statements: *Black* will -always emit an extra empty line after ``return``, ``raise``, ``break``, -``continue``, and ``yield``. This is to make changes in control flow -more prominent to readers of your code. +
+A compatible `.isort.cfg` -That's it. The rest of the whitespace formatting rules follow PEP 8 and -are designed to keep `pycodestyle` quiet. +``` +[settings] +multi_line_output=3 +include_trailing_comma=True +force_grid_wrap=0 +use_parentheses=True +line_length=88 +``` +The equivalent command line is: +``` +$ isort --multi-line=3 --trailing-comma --force-grid-wrap=0 --use-parentheses --line-width=88 [ file.py ] +``` +
### Line length @@ -175,31 +293,668 @@ you are probably already using. You'd do it like this: max-line-length = 80 ... select = C,E,F,W,B,B950 -ignore = E501 +ignore = E501,W503,E203 ``` 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 +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". -### Editor integration +### 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* 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. + +*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. + + +### 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. + + +### 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/python/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`. + + +### 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) +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. + + +### 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. + + +### 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: + +- `if (...):` +- `while (...):` +- `for (...) in (...):` +- `assert (...), (...)` +- `from X import (...)` +- assignments like: + - `target = (...)` + - `target: type = (...)` + - `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: +```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: +```py3 +def example(session): + result = ( + session.query(models.Customer.id) + .filter( + models.Customer.account_id == account_id, + models.Customer.email == email_address, + ) + .order_by(models.Customer.id.asc()) + .all() + ) +``` + + +### 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]`. + + +## 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. + +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` + +```toml +[tool.black] +line-length = 88 +target-version = ['py37'] +include = '\.pyi?$' +exclude = ''' + +( + /( + \.eggs # exclude a few common directories in the + | \.git # root of the project + | \.hg + | \.mypy_cache + | \.tox + | \.venv + | _build + | buck-out + | build + | dist + )/ + | foo.py # also separately exclude a file named foo.py in + # the root of the project +) +''' +``` + +
+ +### Lookup hierarchy + +Command-line options have defaults that you can see in `--help`. +A `pyproject.toml` can override those defaults. Finally, options +provided by the user on the command line override both. + +*Black* will only ever use one `pyproject.toml` file during an entire +run. It doesn't look for multiple files, and doesn't compose +configuration from different levels of the file hierarchy. + + +## Editor integration + +### Emacs + +Use [proofit404/blacken](https://github.com/proofit404/blacken) or +[Elpy](https://github.com/jorgenschaefer/elpy). + + +### PyCharm/IntelliJ IDEA + +1. Install `black`. + +```console +$ pip install black +``` + +2. Locate your `black` installation folder. + + On macOS / Linux / BSD: + +```console +$ which black +/usr/local/bin/black # possible location +``` + + On Windows: + +```console +$ where black +%LocalAppData%\Programs\Python\Python36-32\Scripts\black.exe # possible location +``` + +3. Open External tools in PyCharm/IntelliJ IDEA + + On macOS: + +```PyCharm -> Preferences -> Tools -> External Tools``` + + On Windows / Linux / BSD: + +```File -> Settings -> Tools -> External Tools``` -There is currently no integration with any text editors. Vim and -Atom/Nuclide integration is planned by the author, others will require -external contributions. +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: `"$FilePath$"` + +5. Format the currently opened file by selecting `Tools -> External Tools -> black`. + - 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. + +```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: + +* `: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`) + +To install with [vim-plug](https://github.com/junegunn/vim-plug): + +``` +Plug 'python/black' +``` + +or with [Vundle](https://github.com/VundleVim/Vundle.vim): + +``` +Plugin 'python/black' +``` + +or you can copy the plugin from [plugin/black.vim](https://github.com/python/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. + +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. + + +### Visual Studio Code + +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). + + +### 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 +[pyls-black](https://github.com/rupert/pyls-black) plugin. + + +### Atom/Nuclide + +Use [python-black](https://atom.io/packages/python-black). + + +### Other editors + +Other editors will require external contributions. Patches welcome! ✨ 🍰 ✨ +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. + +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 + +`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`. + +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. + +## 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/python/black + rev: stable + hooks: + - 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](/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 +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\\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 + +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), +every Datadog Agent Integration. + +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): -> 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 +**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! @@ -214,25 +969,21 @@ and [`pipenv`](https://docs.pipenv.org/): > This vastly improves the formatting of our code. Thanks a ton! -## Tests +## Show your style -Just run: +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/python/black) ``` -python setup.py test -``` - -## This tool requires Python 3.6.0+ to run -But you can reformat Python 2 code with it, too. *Black* is able to parse -all of the new syntax supported on Python 3.6 but also *effectively all* -the Python 2 syntax at the same time, as long as you're not using print -statements. +Using the badge in README.rst: +``` +.. image:: https://img.shields.io/badge/code%20style-black-000000.svg + :target: https://github.com/python/black +``` -By making the code exclusively Python 3.6+, I'm able to focus on the -quality of the formatting and re-use all the nice features of the new -releases (check out [pathlib](https://docs.python.org/3/library/pathlib.html) or -f-strings) instead of wasting cycles on Unicode compatibility, and so on. +Looks like this: [![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/python/black) ## License @@ -240,10 +991,10 @@ f-strings) instead of wasting cycles on Unicode compatibility, and so on. MIT -## Contributing +## Contributing to *Black* -In terms of inspiration, *Black* is about as configurable as *gofmt* and -*rustfmt* are. 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 @@ -253,15 +1004,447 @@ 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 +### unreleased + +* added `black -c` as a way to format code passed from the command line + (#761) + +* --safe now works with Python 2 code (#840) + +* fixed grammar selection for Python 2-specific code (#765) + +* fixed feature detection for trailing commas in function definitions + and call sites (#763) + +* *Black* can now format async generators (#593) + +* *Black* no longer crashes on Windows machines with more than 61 cores + (#838) + +* *Black* no longer crashes on standalone comments prepended with + a backslash (#767) + +* *Black* no longer crashes on `from` ... `import` blocks with comments + (#829) + +* removed unnecessary parentheses around `yield` expressions (#834) + +* added parentheses around long tuples in unpacking assignments (#832) + +* fixed bug that led *Black* format some code with a line length target + of 1 (#762) + +* *Black* no longer introduces quotes in f-string subexpressions on string + boundaries (#863) + +* if *Black* puts parenthesis around a single expression, it moves comments + to the wrapped expression instead of after the brackets (#872) + + +### 19.3b0 + +* new option `--target-version` to control which Python versions + *Black*-formatted code should target (#618) + +* deprecated `--py36` (use `--target-version=py36` instead) (#724) + +* *Black* no longer normalizes numeric literals to include `_` separators (#696) + +* long `del` statements are now split into multiple lines (#698) + +* type comments are no longer mangled in function signatures + +* improved performance of formatting deeply nested data structures (#509) + +* *Black* now properly formats multiple files in parallel on + Windows (#632) + +* *Black* now creates cache files atomically which allows it to be used + in parallel pipelines (like `xargs -P8`) (#673) + +* *Black* now correctly indents comments in files that were previously + formatted with tabs (#262) + +* `blackd` now supports CORS (#622) + + +### 18.9b0 + +* numeric literals are now formatted by *Black* (#452, #461, #464, #469): + + * numeric literals are normalized to include `_` separators on Python 3.6+ code + + * added `--skip-numeric-underscore-normalization` to disable the above behavior and + leave numeric underscores as they were in the input + + * code with `_` in numeric literals is recognized as Python 3.6+ + + * most letters in numeric literals are lowercased (e.g., in `1e10`, `0x01`) + + * hexadecimal digits are always uppercased (e.g. `0xBADC0DE`) + +* added `blackd`, see [its documentation](#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) + +* 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 @@ -283,3 +1466,33 @@ You can still try but prepare to be disappointed. ## Authors Glued together by [Łukasz Langa](mailto:lukasz@langa.pl). + +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). + +Multiple contributions by: +* [Anthony Sottile](mailto:asottile@umich.edu) +* [Artem Malyshev](mailto:proofit404@gmail.com) +* [Benjamin Woodruff](mailto:github@benjam.info) +* [Christian Heimes](mailto:christian@python.org) +* [Daniel M. Capella](mailto:polycitizen@gmail.com) +* [Eli Treuherz](mailto:eli@treuherz.com) +* hauntsaninja +* Hugo van Kemenade +* [Ivan Katanić](mailto:ivan.katanic@gmail.com) +* [Jason Fried](mailto:me@jasonfried.info) +* [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) +* [Utsav Shah](mailto:ukshah2@illinois.edu) +* [Vishwas B Sharma](mailto:sharma.vishwas88@gmail.com) +* [Chuck Wooters](mailto:chuck.wooters@microsoft.com)