python code style docs

src/blenderbim/docs/devs/code_style.rst

@@ -0,0 +1,20 @@
+Code style
+============
+
+
+Black code formatter
+-------------------------------
+For Python code formatting, we use `Black code formatter <https://pypi.org/project/black/>`__ with ``--line-length 120``.
+
+``black`` can be installed using ``pip install black`` and files can be formatted with the following example command:
+
+.. code-block:: bash
+
+   black --line-length 120 src/blenderbim/blenderbim/bim/module/qto/operator.py
+
+Using PowerShell, you can run the Black formatter on the last commit in the repository.
+You can change ``~1`` to ``~n`` to affect ``n`` commits.
+
+.. code-block:: powershell
+
+   git diff HEAD HEAD~1 --name-only | where {$_ -like "*.py"} | foreach-object { start $_ && black --line-length 120 $_ }

src/blenderbim/docs/index.rst

@@ -40,6 +40,7 @@ Learn how to model a small building and create simple architectural plans, secti
 
    devs/installation
    devs/hello_world
+   devs/code_style
    devs/running_tests
    devs/writing_docs
    devs/translations