<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.
* 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).
*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,
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.
+
### Line length
*Black* avoids spurious vertical whitespace. This is in the spirit of
PEP 8 which says that in-function vertical whitespace should only be
-used sparingly. One exception is control flow statements: *Black* will
-always emit an extra empty line after ``return``, ``raise``, ``break``,
-``continue``, and ``yield``. This is to make changes in control flow
-more prominent to readers of your code.
+used sparingly.
*Black* will allow single empty lines inside functions, and single and
double empty lines on module level left by the original editors, except
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 put those empty lines also
-between the function definition and any standalone comments that
-immediately precede the given function. If you want to comment on the
-entire function, use a docstring or put a leading comment in the function
-body.
+after module-level functions. *Black* will not put empty lines between
+function/class definitions and standalone comments that immediately precede
+the given function/class.
### Trailing commas
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
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 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
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.
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
is 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.pickle`
-* macOS: `/Users/<username>/Library/Caches/black/<version>/cache.pickle`
-* Linux: `/home/<username>/.cache/black/<version>/cache.pickle`
+* Windows: `C:\\Users\<username>\AppData\Local\black\black\Cache\<version>\cache.<line-length>.pickle`
+* macOS: `/Users/<username>/Library/Caches/black/<version>/cache.<line-length>.pickle`
+* Linux: `/home/<username>/.cache/black/<version>/cache.<line-length>.pickle`
## Testimonials
## 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)
+### 18.5a0 (unreleased)
+
+* call chains are now formatted according to the [fluent interfaces](https://en.wikipedia.org/wiki/Fluent_interface) style (#67)
+
+* 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 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)
* 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
* 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)
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)
+* [Miguel Gaiowski](mailto:miggaiowski@gmail.com)
* [Osaetin Daniel](mailto:osaetindaniel@gmail.com)
+* [Sunil Kapil](mailto:snlkapil@gmail.com)
* [Vishwas B Sharma](mailto:sharma.vishwas88@gmail.com)
projects / etc / vim.git / blobdiff