+- 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]`.
+
+## Pragmatism
+
+Early versions of _Black_ used to be absolutist in some respects. They took after its
+initial author. This was fine at the time as it made the implementation simpler and
+there were not many users anyway. Not many edge cases were reported. As a mature tool,
+_Black_ does make some exceptions to rules it otherwise holds. This section documents
+what those exceptions are and why this is the case.
+
+### The magic trailing comma
+
+_Black_ in general does not take existing formatting into account.
+
+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.
+
+For example:
+
+```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.
+
+**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.
+
+<details>
+<summary>Example `pyproject.toml`</summary>
+
+```toml
+[tool.black]
+line-length = 88
+target-version = ['py37']
+include = '\.pyi?$'
+exclude = '''
+
+(
+ /(
+ \.eggs # exclude a few common directories in the
+ | \.git # root of the project
+ | \.hg
+ | \.mypy_cache
+ | \.tox
+ | \.venv
+ | _build
+ | buck-out
+ | build
+ | dist
+ )/
+ | foo.py # also separately exclude a file named foo.py in
+ # the root of the project
+)
+'''
+```
+
+</details>
+
+### Lookup hierarchy
+
+Command-line options have defaults that you can see in `--help`. A `pyproject.toml` can
+override those defaults. Finally, options provided by the user on the command line
+override both.
+
+_Black_ will only ever use one `pyproject.toml` file during an entire run. It doesn't
+look for multiple files, and doesn't compose configuration from different levels of the
+file hierarchy.
+
+## Editor integration
+
+### Emacs
+
+Use [proofit404/blacken](https://github.com/proofit404/blacken) or
+[Elpy](https://github.com/jorgenschaefer/elpy).
+
+### PyCharm/IntelliJ IDEA
+
+1. Install `black`.
+
+```console
+$ 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`
+
+4. Click the + icon to add a new external tool with the following values:
+
+ - Name: Black
+ - Description: Black is the uncompromising Python code formatter.
+ - Program: <install_location_from_step_2>
+ - Arguments: `"$FilePath$"`
+
+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: <install_location_from_step_2>
+ - 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` or `~/.local/share/nvim/black`)
+
+To install with [vim-plug](https://github.com/junegunn/vim-plug):
+
+```
+Plug 'psf/black'
+```
+
+or with [Vundle](https://github.com/VundleVim/Vundle.vim):
+
+```
+Plugin 'psf/black'
+```
+
+or you can copy the plugin from
+[plugin/black.vim](https://github.com/psf/black/tree/master/plugin/black.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
+```
+
+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'
+```
+
+To run _Black_ on a key press (e.g. F9 below), add this:
+
+```
+nnoremap <F9> :Black<CR>
+```
+
+**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)
+([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).
+
+### 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
+
+Other editors will require external contributions.
projects / etc / vim.git / blobdiff