Package: axblack
The Uncompromising Code Formatter(compromised version)...as long as it's'black'axblack - Default Style"""Module doc axblack style formatted"""deffoo():"""func doc"""# double quotes for docstringss='hello world'# single quotes for codestmt='''SELECT *FROM fooWHERE bar;'''m={'a':'b'}# trailing comma & short line: no line break:print(42,)"""Module doc - psf/black formatted"""deffoo():"""func doc"""s="hello world"stmt="""SELECT *FROM fooWHERE bar;"""m={"a":"b"}# trailing comma => line break *always*print(42,)Also, this older version of black seemsnottochange the AST.This is a forked alternative to the officialblackformatter,
which is a wonderful tool but (too?)strictabout single quotes, (very) unfortunatelly.We we are sure they'll change their minds one day, so this fork is not necessary any more - it is a workaround to bridge that time gap.Note: There are other forks as well, with yet more features, e.g.oitnb- orange is the new black.Thisfork is based onthispsf/black version (2019-11-23). We will not merge in all code restructurings done in 2020.PerformanceThis is based on a python only version of black. Meanwhile they compile it to C, gaining some 25-30% performance, compared to axblack.
You'll notice a difference only at huge file sizes.Tip: Configure your code formatter to runasyncat file save.BackgroundThe argument that one unified stylewouldbe superbeneficial for
the whole community we do share - BUT: While line lengthisstill configurable that goal cannot be reached anyway, even with opinionated fixed quoting style. Also with the new (since 20.x?) 'line wrap at trailing comma feature' they actually allow a lot of individual 'creative freedom', regarding how code looks.The reason why the black authorchanged his mindaway from using single quotes:pull request/75was this example:{MESSAGE.two: "Please don't look over there."}. Wedon'tdo not think, that this example is justifying the strict rejection of the idea of making quoting style even configurable.You are not alone if you prefer single quotes:If you use single-quotes for your strings you are in good company: “People use to really love double quotes. I don’t know why..>>>""""""'what do you  prefer'""""""'what do you  prefer'DeviationsSingle QuotesSingle quotes are default.Patch is based on thisPR.Configured Excludes Always RespectedWhen you explitely specify excludes in a toml file, then we respect themalways- even if a file is given on the CLI.Rationale:The list of files to be formatted are oftendynamicallybuilt, e.g.:black `git diff --name-only --diff-filter=ACM`We must in such cases still respect the exclude list, even if files had been changed
(e.g. from ZODB dumps).Project root kept at path of pyproject.tomlWhen you configure explicitely (via--config) a pyproject.toml file, then
its path will fix the project root, relevant for regex matching the
excludes (see above). Otherwise black would reset the project root per passed
file, which is a problem when it finds e.g. subrepos' .git or .hg folders.Different VersioningNo pre-release foo.herehereherehereregarding why.We leave the calver style versioning scheme, but w/o dots, to indicate that this is not a "real" project.Yes this isPEP-440compatible.
And yes, we (meanwhile) know thatpipenvhas a problem with such versions and^. Here you have to pin it.NotesWe wanted to keep the offset minimal and not deviate more than necessary.Therefore via the vim plugin and also the blackd server you do not have the option to
set double quotes - you have to use the--double-quotescommand line flag as
only way to get them.Should you prefer them for private projects or find them in project policies, by any means, use the official black version then.Q: Why not rename black into axblack to allow coexistance?A: Because black is builtin-supported bymanytools, which rely on that name. Meaning you need seperate python
environments in order to use both on one host.Tip: When a tool has a dependency on the official version than nail it to18.6b4, e.g. in pyproject.toml:[tool.poetry.dev-dependencies]autoflake="^1.4"axblack="^20201010"black="18.6b4"Since axblack still is installed into site-packges directly, while newer
version of black are in a subfolder there.Changelog[2022-03-30 13:33]Removed the_unicodefunpatching of click (https://github.com/axiros/axblack/issues/16)[ 2022-03-21 14:47]Added an unprocessed--stdin-filenameCLI switch, since some LSP servers (e.g. null-ls) send it[2020-10-09 19:31]Changed the triple quote behaviour (keep them only in simple statements like
docstrings but not assignments). Seehttps://github.com/axiros/axblack/issues/6[2019-12-12 12:57]Changed the exclude behaviour: When exclude given in .toml file wealwaysrespect it - even if a file is excplitely given on CLI for formats.[2019-11-24 11:21]Set single_quotes as default in black.pyclass File, so that it works also
in vim.[2019-11-24 11:21]Recreated repo as direct fork of psf/black, with adapted master branch for
easier future merges from them (and getting their newest improvements)[2019-11-23 21:16]Dropped the -s in favor of the long argument "double-quotes" - to never
collide with any argument of theirs. Default for double-quotes: FalseBugfixed the parsing of single-quotesAdded thecftool.[2019-11-23 18:05]Added more README (Usage)[2019-11-23 15:05]Initial version after:git clone https://github.com/mark-riley/black.git axblackgit reset --hard configure-quote-stylegit reset --hard remotes/origin/configure-quote-styleSetdefault=Trueinto black.pyCreated axblack pip and pushed to pypi.Installationpip install axblackinto a python3 v(irtual)env or conda environment.See also original docu below - exchange "psf/black" with "axiros/axblack".Vim SetupInstall black into a python environment and refer to it viag:black_virtualenvas shown in the example, then the plugin will install
a venv into .vim/black!Also, note that it proves very handy to have formatting being done at each file write.Suggested vim setupPlug'axiros/axblack'" not black related but useful:autocmdFileTypepython map<Leader>eOtry:<Esc>j^i<TAB><Esc>oexcept Exceptionasex:<CR>print('breakpoint set')<CR>breakpoint()<CR>keep_ctx=True<Esc>^" defaults:letg:black_linelength=88letg:black_fast=1" set appropriately:letg:black_virtualenv="<set to base dir of a py3 environ with black installed>"" Clean whitespace at saves:"autocmd BufWritePre * execute ':RemoveWhitespace'fun!Blackify()if&ft=~'python':Blackendifendfun" blackify at any write of a python file:autocmdBufWritePre*callBlackify()" Using pythonmode? Keep it happy:letg:pymode_options_max_line_length=88letg:pymode_lint_options_pep8={'max_line_length':g:pymode_options_max_line_length}letg:pymode_options_colorcolumn=1Usage In Projectspyproject.tomlCreate apyproject.tomlfile in the toplevel directory of your project as
shown below and adapt the exclude directories according to your needs.Example `pyproject.toml`Add a note for using axblack to avoid confusion:[tool.black]# using pip install axblack for single_quotesline-length=88target-version=['py27']include='\.pyi?$'exclude='''(/(\.eggs         # exclude a few common directories in the| \.git          # root of the project| \.hg| \.mypy_cache| \.tox| \.venv| _build| build| dist)/| (.*)/foo.py      # also separately exclude a files named foo.py)'''Thenblack .will reformat from the current directory, recursively (not
above this directory).If you have a mix of python2 and python3 in your project then create
a specificpyproject.tomlwithin the respective top level directory and run
black for each of them seperately. black always searching up the specified
directory on the command line for the first project toml file and uses it.Conversion of Large Existing Code BasesBlack ensures to not break anything, by comparing ASTs before and after
formatting - which slows it down a bit.If the code base is large you want to normally havefastmode on, therefore, in daily work.This is what you do:Create your project toml file with excludes which shallneverbe
formattet.Run black with--safeon. If all can be converted then good, you can add--fastfrom now on or put it even into your toml file.Should you have errors from the AST check then,beforeany run in fast mode eitherexclude those files within the tomlfix them. From experience this often hints to bugs.Example:error: cannot format .../sleekxmpp/thirdparty/gnupg.py: INTERNAL ERROR:
Black produced different code on the second pass of the formatter.Again:Do not run black in fast mode if you had errors in safe mode!It will produce source code which is potentially off, behaviourally, from the original!Coding Policy EnforcementWith more collaborateurs on the same repo (e.g. at a customer site) you may want to
consider enforcing your code style via a repo hook:Repo Hook Example# cat .git/hooks/pre-commit#!/bin/sh# We reject any commit for unformatted source code# We can't fix here since we might have partial hunks, which after reformat, which is# global, would differ in the non committed hunks from the state in the FS:black="/agent/py3/bin/black"# adapt to your environmentgitdiff--cached--name-only--diff-filter=ACM|whileread-rfndoecho"Format check:$fn""$black"--check"$fn">/dev/null||exit1echo"Accepted."done||{echo"Commit rejected - not all files formatted correctly."echo"Please do so now:$black-h"exit1}Wrapper ToolIf youcan't adopt pyproject.toml but want to stick to shell sourceable config
and /or environ based configrequire composition of such configeasily want to run in client server mode, for speedrequire automatically created skip liststhen have a look atthiscode formatter tool we created, which
wraps black and blackd.The tool is not installed by pip currently.Original docu follows...:Blackis the uncompromising Python code formatter.  By using it, you
agree to cede control over minutiae of hand-formatting.  In return,Blackgives you speed, determinism, and freedom frompycodestylenagging about formatting.  You will save time and mental energy for
more important matters.Blackened code looks the same regardless of the project you're reading.
Formatting becomes transparent after a while and you can focus on the
content instead.Blackmakes code review faster by producing the smallest diffs
possible.Try it out now using theBlack Playground.
Watch thePyCon 2019 talkto learn more.Contents:Installation and usage|Code style|pyproject.toml|Editor integration|blackd|Version control integration|Ignoring unmodified files|Used by|Testimonials|Show your style|Contributing|Change Log|AuthorsInstallation and usageInstallationBlackcan be installed by runningpip install black.  It requires
Python 3.6.0+ to run but you can reformat Python 2 code with it, too.UsageTo get started right away with sensible defaults:black {source_file_or_directory}Command line optionsBlackdoesn't provide many options.  You can list them by runningblack --help:black [OPTIONS] [SRC]...

Options:
  -c, --code TEXT                 Format the code passed in as a string.
  -l, --line-length INTEGER       How many characters per line to allow.
                                  [default: 88]
  -t, --target-version [py27|py33|py34|py35|py36|py37|py38]
                                  Python versions that should be supported by
                                  Black's output. [default: per-file auto-
                                  detection]
  --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. Deprecated; use
                                  --target-version instead. [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 reformatted.  Return code 123 means
                                  there was an internal error.
  --diff                          Don't write the files back, just output a
                                  diff 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.  An empty value means
                                  all files are included regardless of the
                                  name.  Use forward slashes for directories
                                  on all platforms (Windows, too).  Exclusions
                                  are calculated first, inclusions later.
                                  [default: \.pyi?$]
  --exclude TEXT                  A regular expression that matches files and
                                  directories that should be excluded on
                                  recursive searches.  An empty value means no
                                  paths are excluded. Use forward slashes for
                                  directories on all platforms (Windows, too).
                                  Exclusions are calculated first, inclusions
                                  later.  [default: /(\.eggs|\.git|\.hg|\.mypy
                                  _cache|\.nox|\.tox|\.venv|_build|buck-
                                  out|build|dist)/]
  -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.
  --config PATH                   Read configuration from PATH.
  -h, --help                      Show this message and exit.Blackis a well-behaved Unix-style command-line tool:it does nothing if no sources are passed to it;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 occurred (or--checkwas
used).NOTE: This is a beta productBlackis alreadysuccessfully usedby many 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
"Beta" trove classifier, as well as by the "b" in the version number.
What this means for you is thatuntil the formatter becomes stable,
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,Blackwill 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.TheBlackcode styleBlackreformats entire files in place.  It is not configurable.  It
doesn't take previous formatting into account.  It doesn't reformat
blocks that start with# fmt: offand end with# fmt: on.# fmt: on/offhave to be on the same level of indentation. It also
recognizesYAPF's block comments to
the same effect, as a courtesy for straddling code.HowBlackwraps linesBlackignores previous formatting and applies uniform horizontal
and vertical whitespace to your code.  The rules for horizontal
whitespace can be summarized as: do whatever makespycodestylehappy.
The coding style used byBlackcan be viewed as a strict subset of
PEP 8.As for vertical whitespace,Blacktries to render one full expression
or simple statement per line.  If this fits the allotted line length,
great.# in:l=[1,2,3,]# out:l=[1,2,3]If not,Blackwill look at the contents of the first outer matching
brackets and put that in a separate indented line.# in:ImportantClass.important_method(exc,limit,lookup_lines,capture_locals,extra_argument)# out:ImportantClass.important_method(exc,limit,lookup_lines,capture_locals,extra_argument)If that still doesn't fit the bill, it will decompose the internal
expression further using the same rule, indenting matching brackets
every time.  If the contents of the matching brackets pair are
comma-separated (like an argument list, or a dict literal, and so on)
thenBlackwill first try to keep them on the same line with the
matching brackets.  If that doesn't work, it will put all of them in
separate lines.# in:defvery_important_function(template:str,*variables,file:os.PathLike,engine:str,header:bool=True,debug:bool=False):"""Applies `variables` to the `template` and writes to `file`."""withopen(file,'w')asf:...# out:defvery_important_function(template:str,*variables,file:os.PathLike,engine:str,header:bool=True,debug:bool=False,):"""Applies `variables` to the `template` and writes to `file`."""withopen(file,"w")asf:...You might have noticed that closing brackets are always dedented and
that a trailing comma is always added.  Such formatting produces smaller
diffs; when you add or remove an element, it's always just one line.
Also, having the closing bracket dedented provides a clear delimiter
between two distinct sections of the code that otherwise share the same
indentation level (like the arguments list and the docstring in the
example above).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
makesBlackcompatible withisortwith
the following configuration.A compatible `.isort.cfg`[settings]
multi_line_output=3
include_trailing_comma=True
force_grid_wrap=0
use_parentheses=True
line_length=88The equivalent command line is:$ isort --multi-line=3 --trailing-comma --force-grid-wrap=0 --use-parentheses --line-width=88 [ file.py ]Line lengthYou probably noticed the peculiar default line length.Blackdefaults
to 88 characters per line, which happens to be 10% over 80.  This number
was found to produce significantly shorter files than sticking with 80
(the most popular), or even 79 (used by the standard library).  In
general,90-ish seems like the wise choice.If you're paid by the line of code you write, you can pass--line-lengthwith a lower number.Blackwill try to respect that.
However, sometimes it won't be able to without breaking other rules.  In
those rare cases, auto-formatted code will exceed your allotted limit.You can also increase it, but remember that people with sight disabilities
find it harder to work with line lengths exceeding 100 characters.
It also adversely affects side-by-side diff review  on typical screen
resolutions.  Long lines also make it harder to present code neatly
in documentation or talk slides.If you're using Flake8, you can bumpmax-line-lengthto 88 and forget
about it.  Alternatively, useBugbear's
B950 warning instead of E501 and keep the max line length at 80 which
you are probably already using.  You'd do it like this:[flake8]max-line-length=80...select=C,E,F,W,B,B950ignore=E501,W503,E203You'll findBlack's own .flake8 config file is configured like this.
If you're curious about the reasoning behind B950,Bugbear's documentationexplains it.  The tl;dr is "it's like highway speed limits, we won't
bother you if you overdo it by a few km/h".Empty linesBlackavoids spurious vertical whitespace.  This is in the spirit of
PEP 8 which says that in-function vertical whitespace should only be
used sparingly.Blackwill 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
after module-level functions and classes.Blackwill not put empty
lines between function/class definitions and standalone comments that
immediately precede the given function/class.Blackwill enforce single empty lines between a class-level docstring
and the first following field or method.  This conforms toPEP 257.Blackwon't insert empty lines after function docstrings unless that
empty line is required due to an inner function starting immediately
after.Trailing commasBlackwill 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 caseBlackwon'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.Blackwill 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 andBlackdidn't
recognize it was safe to do so, put it there manually andBlackwill
keep it.StringsBlackprefers 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.Blackalso standardizes string prefixes, making them always lowercase.
On top of that, if your code is already Python 3.6+ only or it's using
theunicode_literalsfuture import,Blackwill removeufrom 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 ofBlackto merge consecutive
string literals that ended up on the same line (see#26for details).Why settle on double quotes?  They anticipate apostrophes in English
text.  They match the docstring standard described inPEP 257.
An empty string in double quotes ("") is impossible to confuse with
a one double-quote regardless of fonts and syntax highlighting used.
On top of this, double quotes for strings are consistent with C which
Python interacts a lot with.On certain keyboard layouts like US English, typing single quotes is
a bit easier than double quotes.  The latter requires use of the Shift
key.  My recommendation here is to keep using whatever is faster to type
and letBlackhandle the transformation.If you are adoptingBlackin a large project with pre-existing string
conventions (like the popular"single quotes for data, double quotes for
human-readable strings"), you can
pass--skip-string-normalizationon the command line.  This is meant as
an adoption helper, avoid using this for new projects.Numeric literalsBlackstandardizes most numeric literals to use lowercase letters for the
syntactic parts and uppercase letters for the digits themselves:0xABinstead of0XABand1e10instead of1E10. Python 2 long literals are
styled as2Linstead of2lto avoid confusion betweenland1.Line breaks & binary operatorsBlackwill break a line before a binary operator when splitting a block
of code over multiple lines. This is so thatBlackis compliant with the
recent changes in thePEP 8style guide, which emphasizes that this approach improves readability.This behaviour may raiseW503 line break before binary operatorwarnings in
style guide enforcement tools like Flake8. SinceW503is not PEP 8 compliant,
you should tell Flake8 to ignore these warnings.SlicesPEP 8recommendsto 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 ::]).Blackenforces these rules consistently.This behaviour may raiseE203 whitespace before ':'warnings in style guide
enforcement tools like Flake8. SinceE203is not PEP 8 compliant, you should
tell Flake8 to ignore these warnings.ParenthesesSome parentheses are optional in the Python grammar.  Any expression can
be wrapped in a pair of parentheses to form an atom.  There are a few
interesting cases:if (...):while (...):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.  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 thatBlackdoes 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:returnnot(thisorthat)decision=(maybe.this()andvalues>0)or(maybe.that()andvalues<0)Call chainsSome popular APIs, like ORMs, use call chaining.  This API style is known
as afluent interface.Blackformats 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:defexample(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 filesPEP 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.pyifile
extensioncan 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.Blackenforces the above rules.  There are additional guidelines for
formatting.pyifile 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...overpass;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 withfrom __future__ import annotations);use variable annotations instead of type comments, even for stubs that
target older versions of Python;for arguments that default toNone, useOptional[]explicitly;usefloatinstead ofUnion[int, float].pyproject.tomlBlackis able to read project-specific default values for its
command line options from apyproject.tomlfile.  This is
especially useful for specifying custom--includeand--excludepatterns for your project.Pro-tip: If you're asking yourself "Do I need to configure anything?"
the answer is "No".Blackis all about sensible defaults.What on Earth is apyproject.tomlfile?PEP 518definespyproject.tomlas a configuration file to store build system
requirements for Python projects.  With the help of tools
likePoetryorFlitit can fully replace the
need forsetup.pyandsetup.cfgfiles.WhereBlacklooks for the fileBy defaultBlacklooks forpyproject.tomlstarting 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.gitdirectory, or a.hgdirectory,
or the root of the file system, whichever comes first.If you're formatting standard input,Blackwill 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 situationBlackwill 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 noteblackdwill not usepyproject.tomlconfiguration.Configuration formatAs the file extension suggests,pyproject.tomlis aTOMLfile.  It contains separate
sections for different tools.Blackis 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.Example `pyproject.toml`[tool.black]line-length=88target-version=['py37']include='\.pyi?$'exclude='''(/(\.eggs         # exclude a few common directories in the| \.git          # root of the project| \.hg| \.mypy_cache| \.tox| \.venv| _build| buck-out| build| dist)/| foo.py           # also separately exclude a file named foo.py in# the root of the project)'''Lookup hierarchyCommand-line options have defaults that you can see in--help.
Apyproject.tomlcan override those defaults.  Finally, options
provided by the user on the command line override both.Blackwill only ever use onepyproject.tomlfile during an entire
run. It doesn't look for multiple files, and doesn't compose
configuration from different levels of the file hierarchy.Editor integrationEmacsUseproofit404/blackenorElpy.PyCharm/IntelliJ IDEAInstallblack.$pipinstallblackLocate yourblackinstallation folder.On macOS / Linux / BSD:$whichblack/usr/local/bin/black  # possible locationOn Windows:$whereblack%LocalAppData%\Programs\Python\Python36-32\Scripts\black.exe# possible locationOpen External tools in PyCharm/IntelliJ IDEAOn macOS:PyCharm -> Preferences -> Tools -> External ToolsOn Windows / Linux / BSD:File -> Settings -> Tools -> External ToolsClick the + icon to add a new external tool with the following values:Name: BlackDescription: Black is the uncompromising Python code formatter.Program: <install_location_from_step_2>Arguments:"$FilePath$"Format the currently opened file by selectingTools -> External Tools -> black.Alternatively, you can set a keyboard shortcut by navigating toPreferences or Settings -> Keymap -> External Tools -> External Tools - Black.Optionally, runBlackon every file save:Make sure you have theFile Watcherplugin installed.Go toPreferences or Settings -> Tools -> File Watchersand click+to add a new watcher:Name: BlackFile type: PythonScope: Project FilesProgram: <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 IDEWing supports black via the OS Commands tool, as explained in the Wing documentation onpep8 formatting. The detailed procedure is:Installblack.$pipinstallblackMake sure it runs from the command line, e.g.$black--helpIn Wing IDE, activate theOS Commandspanel  and define the commandblackto execute black on the currently selected file:Use the Tools -> OS Commands menu selectionclick on+inOS Commands-> New: Command line..Title: blackCommand Line: black %sI/O Encoding: Use DefaultKey Binding: F1Raise OS Commands when executedAuto-save files before executionLine modeSelect a file in the editor and pressF1, or whatever key binding you selected in step 3, to reformat the file.VimCommands and shortcuts::Blackto format the entire file (ranges not supported);:BlackUpgradeto upgradeBlackinside the virtualenv;:BlackVersionto get the current version ofBlackinside the
virtualenv.Configuration:g:black_fast(defaults to0)g:black_linelength(defaults to88)g:black_skip_string_normalization(defaults to0)g:black_virtualenv(defaults to~/.vim/black)To install withvim-plug:Plug 'psf/black'or withVundle:Plugin 'psf/black'or you can copy the plugin fromplugin/black.vim.
Let me know if this requires any changes to work with Vim 8's builtinpackadd, or Pathogen, and so on.This pluginrequires Vim 7.0+ built with Python 3.6+ support.  It
needs Python 3.6 to be able to runBlackinside 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 installsBlack. You can upgrade it later
by calling:BlackUpgradeand restarting Vim.If you need to do anything special to make your virtualenv work and
installBlack(for example you want to run a version from master),
create a virtualenv manually and pointg:black_virtualenvto it.
The plugin will use it.To runBlackon save, add the following line to.vimrcorinit.vim:autocmd BufWritePre *.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.
When building Vim from source, use:./configure --enable-python3interp=yes. There's many guides online how
to do this.Visual Studio CodeUse thePython extension(instructions).SublimeText 3Usesublack plugin.Jupyter Notebook MagicUseblackcellmagic.Python Language ServerIf your editor supports theLanguage Server Protocol(Atom, Sublime Text, Visual Studio Code and many more), you can use
thePython Language Serverwith thepyls-blackplugin.Atom/NuclideUsepython-black.Other editorsOther editors will require external contributions.Patches welcome! ✨ 🍰 ✨Any tool that can pipe code throughBlackusing its stdio mode (justuse-as the file name).
The formatted code will be returned on stdout (unless--checkwas
passed).Blackwill still emit messages on stderr but that shouldn't
affect your use case.This can be used for example with PyCharm's or IntelliJ'sFile Watchers.blackdblackdis a small HTTP server that exposesBlack's functionality over
a simple protocol. The main benefit of using it is to avoid paying the
cost of starting up a newBlackprocess every time you want to blacken
a file.Usageblackdis not packaged alongsideBlackby default because it has additional
dependencies. You will need to dopip install black[d]to install it.You can start the server on the default port, binding only to the local interface
by runningblackd. You will see a single line mentioning the server's version,
and the host and port it's listening on.blackdwill then print an access log
similar to most web servers on standard output, merged with any exception traces
caused by invalid formatting requests.blackdprovides even less options thanBlack. You can see them by runningblackd --help:Usage: blackd [OPTIONS]

Options:
  --bind-host TEXT                Address to bind the server to.
  --bind-port INTEGER             Port to listen on
  --version                       Show the version and exit.
  -h, --help                      Show this message and exit.There is no official blackd client tool (yet!). You can test that blackd is
working usingcurl:blackd --bind-port 9090 &  # or let blackd choose a port
curl -s -XPOST "localhost:9090" -d "print('valid')"Protocolblackdonly acceptsPOSTrequests at the/path. The body of the request
should contain the python source code to be formatted, encoded
according to thecharsetfield in theContent-Typerequest header. If nocharsetis specified,blackdassumesUTF-8.There are a few HTTP headers that control how the source is formatted. These
correspond to command line flags forBlack. There is one exception to this:X-Protocol-Versionwhich if present, should have the value1, otherwise the
request is rejected withHTTP 501(Not Implemented).The headers controlling how code is formatted are:X-Line-Length: corresponds to the--line-lengthcommand line flag.X-Skip-String-Normalization: corresponds to the--skip-string-normalizationcommand line flag. If present and its value is not the empty string, no string
normalization will be performed.X-Fast-Or-Safe: if set tofast,blackdwill act asBlackdoes when
passed the--fastcommand line flag.X-Python-Variant: if set topyi,blackdwill act asBlackdoes when
passed the--pyicommand line flag. Otherwise, its value must correspond to
a Python version or a set of comma-separated Python versions, optionally
prefixed withpy. For example, to request code that is compatible
with Python 3.5 and 3.6, set the header topy3.5,py3.6.If any of these headers are set to invalid values,blackdreturns aHTTP 400error response, mentioning the name of the problematic header in the message body.Apart from the above,blackdcan produce the following response codes:HTTP 204: If the input is already well-formatted. The response body is
empty.HTTP 200: If formatting was needed on the input. The response body
contains the blackened Python code, and theContent-Typeheader is set
accordingly.HTTP 400: If the input contains a syntax error. Details of the error are
returned in the response body.HTTP 500: If there was any kind of error while trying to format the input.
The response body contains a textual representation of the error.Version control integrationUsepre-commit. Once youhave it
installed, add this to the.pre-commit-config.yamlin your repository:repos:-repo:https://github.com/psf/blackrev:stablehooks:-id:blacklanguage_version:python3.6Then runpre-commit installand you're ready to go.Avoid usingargsin the hook.  Instead, store necessary configuration
inpyproject.tomlso that editors and command-line usage of Black all
behave consistently for your project.  SeeBlack's ownpyproject.tomlfor an example.If you're already using Python 3.7, switch thelanguage_versionaccordingly. Finally,stableis a tag that is pinned to the latest
release on PyPI.  If you'd rather run on master, this is also an option.Ignoring unmodified filesBlackremembers files it has already formatted, unless the--diffflag is used or
code is passed via standard input. This information is stored per-user. The exact
location of the file depends on theBlackversion and the system on whichBlackis run. The file is non-portable. The standard location on common operating systems
is:Windows:C:\\Users\<username>\AppData\Local\black\black\Cache\<version>\cache.<line-length>.<file-mode>.picklemacOS:/Users/<username>/Library/Caches/black/<version>/cache.<line-length>.<file-mode>.pickleLinux:/home/<username>/.cache/black/<version>/cache.<line-length>.<file-mode>.picklefile-modeis an int flag that determines whether the file was formatted as 3.6+ only,
as .pyi, and whether string normalization was omitted.To override the location of these files on macOS or Linux, set the environment variableXDG_CACHE_HOMEto your preferred location. For example, if you want to put the cache in
the directory you're runningBlackfrom, setXDG_CACHE_HOME=.cache.Blackwill then
write the above files to.cache/black/<version>/.Used byThe following notable open-source projects trustBlackwith enforcing
a consistent code style: pytest, tox, Pyramid, Django Channels, Hypothesis,
attrs, SQLAlchemy, Poetry, PyPA applications (Warehouse, Pipenv, virtualenv),
every Datadog Agent Integration.Are we missing anyone?  Let us know.TestimonialsDusty Phillips,writer:Blackis opinionated so you don't have to be.Hynek Schlawack,creator ofattrs, core
developer of Twisted and CPython:An auto-formatter that doesn't suck is all I want for Xmas!Carl Meyer,Djangocore developer:At least the name is good.Kenneth Reitz, creator ofrequestsandpipenv:This vastly improves the formatting of our code. Thanks a ton!Show your styleUse the badge in your project's README.md:[![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)Using the badge in README.rst:.. image:: https://img.shields.io/badge/code%20style-black-000000.svg
    :target: https://github.com/psf/blackLooks like this:LicenseMITContributing toBlackIn terms of inspiration,Blackis about as configurable asgofmt.
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
enables better integration with some workflow, fixes an inconsistency,
speeds things up, and so on - go for it!  On the other hand, if your
answer is "because I don't like a particular formatting" then you're not
ready to embraceBlackyet. Such changes are unlikely to get accepted.
You can still try but prepare to be disappointed.More details can be found inCONTRIBUTING.Change Logunreleasedaddedblack -cas 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)Blackcan now format async generators (#593)Blackno longer crashes on Windows machines with more than 61 cores
(#838)Blackno longer crashes on standalone comments prepended with
a backslash (#767)Blackno longer crashes onfrom...importblocks with comments
(#829)removed unnecessary parentheses aroundyieldexpressions (#834)added parentheses around long tuples in unpacking assignments (#832)fixed bug that ledBlackformat some code with a line length target
of 1 (#762)Blackno longer introduces quotes in f-string subexpressions on string
boundaries (#863)ifBlackputs parenthesis around a single expression, it moves comments
to the wrapped expression instead of after the brackets (#872)Blackis now able to format Python code that uses assignment expressions
(:=as described in PEP-572) (#935)Blackis now able to format Python code that uses positional-only
arguments (/as described in PEP-570) (#946)19.3b0new option--target-versionto control which Python versionsBlack-formatted code should target (#618)deprecated--py36(use--target-version=py36instead) (#724)Blackno longer normalizes numeric literals to include_separators (#696)longdelstatements are now split into multiple lines (#698)type comments are no longer mangled in function signaturesimproved performance of formatting deeply nested data structures (#509)Blacknow properly formats multiple files in parallel on
Windows (#632)Blacknow creates cache files atomically which allows it to be used
in parallel pipelines (likexargs -P8) (#673)Blacknow correctly indents comments in files that were previously
formatted with tabs (#262)blackdnow supports CORS (#622)18.9b0numeric literals are now formatted byBlack(#452, #461, #464, #469):numeric literals are normalized to include_separators on Python 3.6+ codeadded--skip-numeric-underscore-normalizationto disable the above behavior and
leave numeric underscores as they were in the inputcode with_in numeric literals is recognized as Python 3.6+most letters in numeric literals are lowercased (e.g., in1e10,0x01)hexadecimal digits are always uppercased (e.g.0xBADC0DE)addedblackd, seeits documentationfor 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--checkis 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 manglingpweaveandSpyder IDEspecial comments (#532)fixed unstable formatting when unpacking big tuples (#267)fixed parsing of__future__imports with renames (#389)fixed scope of# fmt: offwhen directly precedingyieldand other nodes (#385)fixed formatting of lambda expressions with default arguments (#468)fixedasync forstatements:Blackno 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)18.6b4hotfix: don't freeze when multiple comments directly precede# fmt: off(#371)18.6b3typing stub files (.pyi) now have blank lines added after constants (#340)# fmt: offand# fmt: onare 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 filefixed unnecessary slowdown on AST nodes with very many siblingsfixed cannibalizing backslashes during string normalizationfixed a crash due to symbolic links pointing outside of the project directory (#338)18.6b2added--config(#65)added-hequivalent to--help(#316)fixed improper unmodified file caching when-Swas usedfixed extra space in string unpacking (#305)fixed formatting of empty triple quoted strings (#313)fixed unnecessary slowdown in comment placement calculation on lines without
comments18.6b1hotfix: don't output human-facing information on stdout (#299)hotfix: don't output cake emoji on non-zero return code (#300)18.6b0added--includeand--exclude(#270)added--skip-string-normalization(#118)added--verbose(#283)the header output in--diffnow actually conforms to the unified diff specfixed 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)Blacknow preserves line endings when formatting a file in place (#258)18.5b1added--pyi(#249)added--py36(#249)Python grammar pickle caches are stored with the formatting caches, makingBlackwork in environments where site-packages is not user-writable (#192)Blacknow enforces a PEP 257 empty line after a class-level docstring
(and/or fields) and the first methodfixed 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: offsections (#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)18.5b0call chains are now formatted according to thefluent interfacesstyle (#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 anduis removed
on Python 3.6+ only code and Python 2.7+ code with theunicode_literalsfuture 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 incrementallyfixed 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 namefixed 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 purposesfixed crash when dead symlinks where encountered18.4a4don't populate the cache on--check(#175)18.4a3added a "cache"; files already reformatted that haven't changed on disk
won't be reformatted again (#109)--checkand--diffare no longer mutually exclusive (#149)generalized star expression handling, including double stars; this
fixes multiplication making expressions "unsafe" for trailing commas (#132)Blackno longer enforces putting empty lines behind control flow statements
(#90)Blacknow 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--diffnot 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)18.4a2fixed parsing of unaligned standalone comments (#99, #112)fixed placement of dictionary unpacking inside dictionary literals (#111)Vim plugin now works on Windows, toofixed unstable formatting when encountering unnecessarily escaped quotes
in a string (#120)18.4a1added--quiet(#78)added automatic parentheses management (#4)addedpre-commitintegration (#103, #104)fixed reporting on--checkwith multiple files (#101, #102)fixed removing backslash escapes from raw strings (#100, #105)18.4a0added--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;Blackwill 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: disableusage as trailing comment
would causeBlackto not emit the rest of the file (#95)when CTRL+C is pressed while formatting many files,Blackno longer
freaks out with a flurry of asyncio-related exceptionsonly allow up to two empty lines on module level and only single empty
lines within functions (#74)18.3a4# fmt: offand# fmt: onare 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 inSphinx auto-attribute comments(#68)18.3a3don'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 ofasyncas
a name (#20, #42)even better handling of numpy-style array indexing (#33, again)18.3a2changed positioning of binary operators to occur at beginning of lines
instead of at the end, followinga recent change to PEP 8(#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 callif top level functions were separated by a comment, don't put four
empty lines after the upper functionfixed unstable formatting of newlines with importsfixed 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)18.3a1added--checkonly 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*argsor**kwargsused 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)18.3a0first published version, Happy 🍰 Day 2018!alpha qualitydate-versioned (see:https://calver.org/)AuthorsGlued together byŁukasz Langa.Maintained withCarol Willing,Carl Meyer,Jelle Zijlstra,Mika Naylor, andZsolt Dollenstein.Multiple contributions by:Anthony SottileArtem MalyshevBenjamin WoodruffChristian HeimesDaniel M. CapellaEli TreuherzhauntsaninjaHugo van KemenadeIvan KatanićJason FriedJonas ObristLuka SterbicMiguel GaiowskiMiroslav ShubernetskiyNerasteOsaetin DanielPeter BengtssonStavros KorokithakisSunil KapilUtsav ShahVishwas B SharmaChuck Wooters