---
_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)** |
+**[Code style](#the-black-code-style)** | **[Pragmatism](#pragmatism)** |
+**[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)**
- 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
To install with [vim-plug](https://github.com/junegunn/vim-plug):
```
-Plug 'psf/black'
+Plug 'psf/black', { 'branch': 'stable' }
```
or with [Vundle](https://github.com/VundleVim/Vundle.vim):
Plugin 'psf/black'
```
+and execute the following in a terminal:
+
+```console
+$ cd ~/.vim/bundle/black
+$ git checkout origin/stable -b stable
+```
+
or you can copy the plugin from
-[plugin/black.vim](https://github.com/psf/black/tree/master/plugin/black.vim).
+[plugin/black.vim](https://github.com/psf/black/blob/stable/plugin/black.vim).
```
mkdir -p ~/.vim/pack/python/start/black/plugin
```
**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.
+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
## Change Log
-### 19.10b0
-
-- added support for PEP 572 assignment expressions (#711)
-
-- added support for PEP 570 positional-only arguments (#943)
-
-- added support for async generators (#593)
-
-- added support for pre-splitting collections by putting an explicit trailing comma
- inside (#826)
-
-- 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)
-
-- `# fmt: off`/`# fmt: on` comment pairs placed multiple times within the same block of
- code now behave correctly (#1005)
-
-- _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)
-
-- _Black_ no longer crashes on Python 3.7 on some platform configurations (#494)
-
-- _Black_ no longer fails on comments in from-imports (#671)
-
-- _Black_ no longer fails when the file starts with a backslash (#922)
-
-- _Black_ no longer merges regular comments with type comments (#1027)
-
-- _Black_ no longer splits long lines that contain type comments (#997)
-
-- removed unnecessary parentheses around `yield` expressions (#834)
-
-- added parentheses around long tuples in unpacking assignments (#832)
-
-- added parentheses around complex powers when they are prefixed by a unary operator
- (#646)
-
-- 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)
-
-- `blackd` now returns the version of _Black_ in the response headers (#1013)
-
-- `blackd` can now output the diff of formats on source code when the `X-Diff` header is
- provided (#969)
-
-### 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 arguments (#14, #17)
-
-- fixed spurious space after unary operators when the operand was a complex expression
- (#15)
-
-### 18.3a0
-
-- first published version, Happy 🍰 Day 2018!
-
-- alpha quality
+The log's become rather long. It moved to its own file.
-- date-versioned (see: https://calver.org/)
+See [CHANGES](CHANGES.md).
## Authors
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).
+[Mika Naylor](mailto:mail@autophagy.io),
+[Zsolt Dollenstein](mailto:zsol.zsol@gmail.com), and
+[Cooper Lees](mailto:me@cooperlees.com).
Multiple contributions by:
-- [Abdur-Rahmaan Janhangeer](mailto:cryptolabour@gmail.com)
+- [Abdur-Rahmaan Janhangeer](mailto:arj.python@gmail.com)
- [Adam Johnson](mailto:me@adamj.eu)
- [Alexander Huynh](mailto:github@grande.coffee)
- [Andrew Thorp](mailto:andrew.thorp.dev@gmail.com)
- Charles Reid
- [Christian Heimes](mailto:christian@python.org)
- [Chuck Wooters](mailto:chuck.wooters@microsoft.com)
+- [Cooper Ry Lees](mailto:me@cooperlees.com)
- [Daniel Hahler](mailto:github@thequod.de)
- [Daniel M. Capella](mailto:polycitizen@gmail.com)
- Daniele Esposti
projects / etc / vim.git / blobdiff