Jupyter notebook support (#2357)

[etc/vim.git] / docs / faq.md

diff --git a/docs/faq.md b/docs/faq.md
index 46e459883ed91dd3e6829f25a6013a2574c137fb..d7e6a16351fb2e901de0c28faea3f667d588c589 100644 (file)
--- a/docs/faq.md
+++ b/docs/faq.md
@@ -21,7 +21,8 @@ _Black_ is still in [beta](index.rst), some edges are still a bit rough. To comb
 issues, the equivalence of code after formatting is
 [checked](the_black_code_style/current_style.md#ast-before-and-after-formatting) with
 limited special cases where the code is allowed to differ. If issues are found, an error
-is raised and the file is left untouched.
+is raised and the file is left untouched. Magical comments that influence linters and
+other tools, such as `# noqa`, may be moved by _Black_. See below for more details.
 
 ## How stable is Black's style?
 
@@ -36,6 +37,29 @@ Most likely because it is ignored in `.gitignore` or excluded with configuration
 [file collection and discovery](usage_and_configuration/file_collection_and_discovery.md)
 for details.
 
+## Why is my Jupyter Notebook cell not formatted?
+
+_Black_ is timid about formatting Jupyter Notebooks. Cells containing any of the
+following will not be formatted:
+
+- automagics (e.g. `pip install black`)
+- multiline magics, e.g.:
+
+  ```python
+  %timeit f(1, \
+          2, \
+          3)
+  ```
+
+- code which `IPython`'s `TransformerManager` would transform magics into, e.g.:
+
+  ```python
+  get_ipython().system('ls')
+  ```
+
+- invalid syntax, as it can't be safely distinguished from automagics in the absense of
+  a running `IPython` kernel.
+
 ## Why are Flake8's E203 and W503 violated?
 
 Because they go against PEP 8. E203 falsely triggers on list
@@ -50,3 +74,11 @@ For formatting, yes! [Install](getting_started.md#installation) with the `python
 to format Python 2 files too! There are no current plans to drop support, but most
 likely it is bound to happen. Sometime. Eventually. In terms of running _Black_ though,
 Python 3.6 or newer is required.
+
+## Why does my linter or typechecker complain after I format my code?
+
+Some linters and other tools use magical comments (e.g., `# noqa`, `# type: ignore`) to
+influence their behavior. While Black does its best to recognize such comments and leave
+them in the right place, this detection is not and cannot be perfect. Therefore, you'll
+sometimes have to manually move these comments to the right place after you format your
+codebase with _Black_.