* 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).
```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
+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/). Use
+`multi_line_output=3`, `include_trailing_comma=True`,
+`force_grid_wrap=0`, and `line_length=88` in your isort config.
### Line length
recognize it was safe to do so, put it there manually and *Black* will
keep it.
+
### Strings
*Black* prefers double quotes (`"` and `"""`) over single quotes (`'`
and `'''`). It will replace the latter with the former as long as it
does not result in more backslash escapes than before.
+*Black* also standardizes string prefixes, making them always lowercase.
+On top of that, if your code is already Python 3.6+ only or it's using
+the `unicode_literals` future import, *Black* will remove `u` from the
+string prefix as it is meaningless in those scenarios.
+
The main reason to standardize on a single form of quotes is aesthetics.
Having one kind of quotes everywhere reduces reader distraction.
It will also enable a future version of *Black* to merge consecutive
key. My recommendation here is to keep using whatever is faster to type
and let *Black* handle the transformation.
+
### Line Breaks & Binary Operators
*Black* will break a line before a binary operator when splitting a block
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 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
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
### 18.5a0 (unreleased)
+* 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
* 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
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
* [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