*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.
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
```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`,
-`include_trailing_comma=True`, `force_grid_wrap=0`, and `line_length=88` 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 (`'`
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)
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
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
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
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
## Change Log
-### 18.5a0 (unreleased)
+### 18.6b0
+
+* added `--include` and `--exclude` (#270)
+
+* added `--skip-string-normalization` (#118)
+
+* fixed stdin handling not working correctly if an old version of Click was
+ used (#276)
+
+
+### 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)
* 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
* 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
* [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