All patches and comments are welcome. Please squash your changes to logical
commits before using git-format-patch and git-send-email to
patches@git.madduck.net.
If you'd read over the Git project's submission guidelines and adhered to them,
I'd be especially grateful.
1 # Frequently Asked Questions
3 The most common questions and issues users face are aggregated to this FAQ.
8 :class: this-will-duplicate-information-and-it-is-still-useful-here
11 ## Why spaces? I prefer tabs
13 PEP 8 recommends spaces over tabs, and they are used by most of the Python community.
14 _Black_ provides no options to configure the indentation style, and requests for such
15 options will not be considered.
17 However, we recognise that using tabs is an accessibility issue as well. While the
18 option will never be added to _Black_, visually impaired developers may find conversion
19 tools such as `expand/unexpand` (for Linux) useful when contributing to Python projects.
20 A workflow might consist of e.g. setting up appropriate pre-commit and post-merge git
21 hooks, and scripting `unexpand` to run after applying _Black_.
23 ## Does Black have an API?
25 Not yet. _Black_ is fundamentally a command line tool. Many
26 [integrations](/integrations/index.md) are provided, but a Python interface is not one
27 of them. A simple API is being [planned](https://github.com/psf/black/issues/779)
30 ## Is Black safe to use?
32 Yes. _Black_ is strictly about formatting, nothing else. Black strives to ensure that
33 after formatting the AST is
34 [checked](the_black_code_style/current_style.md#ast-before-and-after-formatting) with
35 limited special cases where the code is allowed to differ. If issues are found, an error
36 is raised and the file is left untouched. Magical comments that influence linters and
37 other tools, such as `# noqa`, may be moved by _Black_. See below for more details.
39 ## How stable is Black's style?
41 Stable. _Black_ aims to enforce one style and one style only, with some room for
42 pragmatism. See [The Black Code Style](the_black_code_style/index.md) for more details.
44 Starting in 2022, the formatting output will be stable for the releases made in the same
45 year (other than unintentional bugs). It is possible to opt-in to the latest formatting
46 styles, using the `--preview` flag.
48 ## Why is my file not formatted?
50 Most likely because it is ignored in `.gitignore` or excluded with configuration. See
51 [file collection and discovery](usage_and_configuration/file_collection_and_discovery.md)
54 ## Why is my Jupyter Notebook cell not formatted?
56 _Black_ is timid about formatting Jupyter Notebooks. Cells containing any of the
57 following will not be formatted:
59 - automagics (e.g. `pip install black`)
60 - non-Python cell magics (e.g. `%%writefile`). These can be added with the flag
61 `--python-cell-magics`, e.g. `black --python-cell-magics writefile hello.ipynb`.
62 - multiline magics, e.g.:
70 - code which `IPython`'s `TransformerManager` would transform magics into, e.g.:
73 get_ipython().system('ls')
76 - invalid syntax, as it can't be safely distinguished from automagics in the absence of
77 a running `IPython` kernel.
79 ## Why are Flake8's E203 and W503 violated?
81 Because they go against PEP 8. E203 falsely triggers on list
82 [slices](the_black_code_style/current_style.md#slices), and adhering to W503 hinders
83 readability because operators are misaligned. Disable W503 and enable the
84 disabled-by-default counterpart W504. E203 should be disabled while changes are still
85 [discussed](https://github.com/PyCQA/pycodestyle/issues/373).
87 ## Which Python versions does Black support?
89 Currently the runtime requires Python 3.7-3.11. Formatting is supported for files
90 containing syntax from Python 3.3 to 3.11. We promise to support at least all Python
91 versions that have not reached their end of life. This is the case for both running
92 _Black_ and formatting code.
94 Support for formatting Python 2 code was removed in version 22.0. While we've made no
95 plans to stop supporting older Python 3 minor versions immediately, their support might
96 also be removed some time in the future without a deprecation period.
98 Runtime support for 3.6 was removed in version 22.10.0.
100 ## Why does my linter or typechecker complain after I format my code?
102 Some linters and other tools use magical comments (e.g., `# noqa`, `# type: ignore`) to
103 influence their behavior. While Black does its best to recognize such comments and leave
104 them in the right place, this detection is not and cannot be perfect. Therefore, you'll
105 sometimes have to manually move these comments to the right place after you format your
106 codebase with _Black_.
108 ## Can I run Black with PyPy?
110 Yes, there is support for PyPy 3.7 and higher.
112 ## Why does Black not detect syntax errors in my code?
114 _Black_ is an autoformatter, not a Python linter or interpreter. Detecting all syntax
115 errors is not a goal. It can format all code accepted by CPython (if you find an example
116 where that doesn't hold, please report a bug!), but it may also format some code that
117 CPython doesn't accept.
119 (labels/mypyc-support)=
121 ## What is `compiled: yes/no` all about in the version output?
123 While _Black_ is indeed a pure Python project, we use [mypyc] to compile _Black_ into a
124 C Python extension, usually doubling performance. These compiled wheels are available
125 for 64-bit versions of Windows, Linux (via the manylinux standard), and macOS across all
126 supported CPython versions.
128 Platforms including musl-based and/or ARM Linux distributions, and ARM Windows are
129 currently **not** supported. These platforms will fall back to the slower pure Python
130 wheel available on PyPI.
132 If you are experiencing exceptionally weird issues or even segfaults, you can try
133 passing `--no-binary black` to your pip install invocation. This flag excludes all
134 wheels (including the pure Python wheel), so this command will use the [sdist].
136 [mypyc]: https://mypyc.readthedocs.io/en/latest/
138 https://packaging.python.org/en/latest/glossary/#term-Source-Distribution-or-sdist