<p align="center">
<a href="https://travis-ci.org/ambv/black"><img alt="Build Status" src="https://travis-ci.org/ambv/black.svg?branch=master"></a>
-<a href="http://black.readthedocs.io/en/latest/?badge=latest"><img alt="Documentation Status" src="http://readthedocs.org/projects/black/badge/?version=latest"></a>
+<a href="http://black.readthedocs.io/en/stable/?badge=stable"><img alt="Documentation Status" src="http://readthedocs.org/projects/black/badge/?version=stable"></a>
<a href="https://coveralls.io/github/ambv/black?branch=master"><img alt="Coverage Status" src="https://coveralls.io/repos/github/ambv/black/badge.svg?branch=master"></a>
-<a href="https://github.com/ambv/black/blob/master/LICENSE"><img alt="License: MIT" src="http://black.readthedocs.io/en/latest/_static/license.svg"></a>
-<a href="https://pypi.python.org/pypi/black"><img alt="PyPI" src="http://black.readthedocs.io/en/latest/_static/pypi.svg"></a>
+<a href="https://github.com/ambv/black/blob/master/LICENSE"><img alt="License: MIT" src="http://black.readthedocs.io/en/stable/_static/license.svg"></a>
+<a href="https://pypi.python.org/pypi/black"><img alt="PyPI" src="http://black.readthedocs.io/en/stable/_static/pypi.svg"></a>
<a href="https://github.com/ambv/black"><img alt="Code style: black" src="https://img.shields.io/badge/code%20style-black-000000.svg"></a>
</p>
*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.
*Black* makes code review faster by producing the smallest diffs
possible.
+---
-## Installation and Usage
+*Contents:* **[Installation and usage](#installation-and-usage)** |
+**[The *Black* code style](#the-black-code-style)** |
+**[Editor integration](#editor-integration)** |
+**[Version control integration](#version-control-integration)** |
+**[Ignoring unmodified files](#ignoring-unmodified-files)** |
+**[Testimonials](#testimonials)** |
+**[Show your style](#show-your-style)** |
+**[License](#license)** |
+**[Contributing](#contributing-to-black)** |
+**[Change Log](#change-log)** |
+**[Authors](#authors)**
+
+---
+
+## Installation and usage
### Installation
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).
+ -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
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.
--help Show this message and exit.
```
* 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 occured (or `--check` was
+* exits with code 0 unless an internal error occurred (or `--check` was
used).
-### NOTE: This is an early pre-release
+### NOTE: This is a beta product
-*Black* can already successfully format itself and the standard library.
+*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
-"Alpha" trove classifier, as well as by the "a" in the version number.
+"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**.
+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
*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. The coding style used by *Black* can be
-viewed as a strict subset of PEP 8.
+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,
```py3
# in:
-l = [[n for n in list_bosses()], [n for n in list_employees()]]
+TracebackException.from_exception(exc, limit, lookup_lines, capture_locals)
# out:
-l = [
- [n for n in list_bosses()], [n for n in list_employees()]
-]
+TracebackException.from_exception(
+ exc, limit, lookup_lines, capture_locals
+)
```
If that still doesn't fit the bill, it will decompose the internal
indentation level (like the arguments list and the docstring in the
example above).
-If a line of "from" imports cannot fit in the allotted length, it's always split
-into one per line. Imports tend to change often and this minimizes diffs, as well
-as enables readers of code to easily find which commit introduced a particular
-import. This exception also makes *Black* compatible with
-[isort](https://pypi.org/p/isort/). Use `multi_line_output=3` and
-`include_trailing_comma=True` in your isort config.
+If a data structure literal (tuple, list, set, dict) or a line of "from"
+imports cannot fit in the allotted length, it's always split into one
+element per line. This minimizes diffs as well as enables readers of
+code to find which commit introduced a particular entry. This also
+makes *Black* compatible with [isort](https://pypi.org/p/isort/) with
+the following configuration.
+
+<details>
+<summary>A compatible `.isort.cfg`</summary>
+
+```
+[settings]
+multi_line_output=3
+include_trailing_comma=True
+force_grid_wrap=0
+combine_as_imports=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 ]
+```
+</details>
### Line length
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. *Black* will not put empty lines between
-function/class definitions and standalone comments that immediately precede
-the given function/class.
+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
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
key. My recommendation here is to keep using whatever is faster to type
and let *Black* handle the transformation.
-### Line Breaks & Binary Operators
+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.
+
+
+### 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
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
- `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. Otherwise, the parentheses are always added.
+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]`.
## Editor integration
1. Install `black`.
- $ pip install black
+```console
+$ pip install black
+```
2. Locate your `black` installation folder.
- On MacOS / Linux / BSD:
+ On macOS / Linux / BSD:
- $ which black
- /usr/local/bin/black # possible location
+```console
+$ which black
+/usr/local/bin/black # possible location
+```
On Windows:
- $ where black
- %LocalAppData%\Programs\Python\Python36-32\Scripts\black.exe # possible location
+```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`.
- 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`.
+ - Alternatively, you can set a keyboard shortcut by navigating to `Preferences -> Keymap -> External Tools -> External Tools - Black`.
### Vim
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
+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 BufWritePost *.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`.
+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.
Use [joslarson.black-vscode](https://marketplace.visualstudio.com/items?itemName=joslarson.black-vscode).
+
### SublimeText 3
Use [sublack plugin](https://github.com/jgirardet/sublack).
+
+### IPython Notebook Magic
+
+Use [blackcellmagic](https://github.com/csurfer/blackcellmagic).
+
+
### Other editors
Atom/Nuclide integration is planned by the author, others will
hooks:
- id: black
args: [--line-length=88, --safe]
- python_version: python3.6
+ language_version: python3.6
```
Then run `pre-commit install` and you're ready to go.
`args` in the above config is optional but shows you how you can change
the line length if you really need to. If you're already using Python
-3.7, switch the `python_version` accordingly. Finally, `stable` is a tag
+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 non-modified files
+## Ignoring unmodified files
-*Black* remembers files it 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
## 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
## Change Log
-### 18.4a3 (unreleased)
+### 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)
* fixed missing splits of ternary expressions (#141)
+
### 18.4a2
* fixed parsing of unaligned standalone comments (#99, #112)
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)
* [Osaetin Daniel](mailto:osaetindaniel@gmail.com)
+* [Stavros Korokithakis](mailto:hi@stavros.io)
+* [Sunil Kapil](mailto:snlkapil@gmail.com)
* [Vishwas B Sharma](mailto:sharma.vishwas88@gmail.com)
+
+---
+
+*Contents:*
+**[Installation and Usage](#installation-and-usage)** |
+**[The *Black* code style](#the-black-code-style)** |
+**[Editor integration](#editor-integration)** |
+**[Version control integration](#version-control-integration)** |
+**[Ignoring unmodified files](#ignoring-unmodified-files)** |
+**[Testimonials](#testimonials)** |
+**[Show your style](#show-your-style)** |
+**[License](#license)** |
+**[Contributing](#contributing-to-black)** |
+**[Change Log](#change-log)** |
+**[Authors](#authors)**
projects / etc / vim.git / blobdiff