possible.
-## NOTE: This is an early pre-release
+## Installation and Usage
-*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**.
-
-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
+### 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* 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.
-## Usage
+### 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:
used).
-## The philosophy behind *Black*
+### 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**.
+
+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
*Black* reformats entire files in place. It is not configurable. It
doesn't take previous formatting into account. It doesn't reformat
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.
+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,
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.
-
-*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.
-
-That's it. The rest of the whitespace formatting rules follow PEP 8 and
-are designed to keep `pycodestyle` quiet.
-
### Line length
### Empty lines
-*Black* will allow single empty lines left by the original editors,
-except when they're added within parenthesized expressions. Since such
-expressions are always reformatted to fit minimal space, this whitespace
-is lost.
+*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.
+
+*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
body.
-### Editor integration
+### 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.
+
+
+## Editor integration
+
+### Emacs
+
+Use [proofit404/blacken](https://github.com/proofit404/blacken).
+
+
+### 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.
+
+Configuration:
+* `g:black_fast` (defaults to `0`)
+* `g:black_linelength` (defaults to `88`)
+* `g:black_virtualenv` (defaults to `~/.vim/black`)
+
+To install, copy the plugin from [vim/plugin/black.vim](https://github.com/ambv/black/tree/master/vim/plugin/black.vim).
+Let me know if this requires any changes to work with Vim 8's builtin
+`packadd`, or Pathogen, or Vundle, and so on.
-* Visual Studio Code: [joslarson.black-vscode](https://marketplace.visualstudio.com/items?itemName=joslarson.black-vscode)
-* Emacs: [proofit404/blacken](https://github.com/proofit404/blacken)
+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), just
+create a virtualenv manually and point `g:black_virtualenv` to it.
+The plugin will use it.
+
+**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 [joslarson.black-vscode](https://marketplace.visualstudio.com/items?itemName=joslarson.black-vscode).
+
+
+### Other editors
+
+Atom/Nuclide integration is planned by the author, others will
+require external contributions.
+
+Patches welcome! ✨ 🍰 ✨
Any tool that can pipe code through *Black* using its stdio mode (just
[use `-` as the file name](http://www.tldp.org/LDP/abs/html/special-chars.html#DASHREF2)).
passed). *Black* will still emit messages on stderr but that shouldn't
affect your use case.
-Vim and Atom/Nuclide integration is planned by the author, others will
-require external contributions.
-
-Patches welcome! ✨ 🍰 ✨
+This can be used for example with PyCharm's [File Watchers](https://www.jetbrains.com/help/pycharm/file-watchers.html).
## Testimonials
MIT
-## Contributing
+## Contributing to Black
In terms of inspiration, *Black* is about as configurable as *gofmt* and
*rustfmt* are. This is deliberate.
## Change Log
+### 18.3a5 (unreleased)
+
+* fixed 18.3a4 regression: don't crash and burn on empty lines with
+ trailing whitespace (#80)
+
+* 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)
## Authors
Glued together by [Łukasz Langa](mailto:lukasz@langa.pl).
+
+Maintained with [Carol Willing](mailto:carolcode@willingconsulting.com)
+and [Carl Meyer](mailto:carl@oddbird.net).
+
+Multiple contributions by:
+* [Artem Malyshev](mailto:proofit404@gmail.com)
+* [Daniel M. Capella](mailto:polycitizen@gmail.com)
+* [Eli Treuherz](mailto:eli.treuherz@cgi.com)
+* Hugo van Kemenade
+* [Mika⠙](mailto:mail@autophagy.io)
+* [Osaetin Daniel](mailto:osaetindaniel@gmail.com)
projects / etc / vim.git / blobdiff