Python code standards

Code style standards for Python

This document outlines the rules for writing Python code across all our Projects.

Code style and formatting

We use Flake8 to check our code for compliance with PEP 8, e.g. with flake8 webapp tests. See the list of Flake8 violations for more information.

We use Black to format our Python code using the option --line-length 79 followed by the folders that we want to format. E.g. black --line-length 79 webapp tests

Optionally, you can use iSort to automatically rearranges your imports in different sections. It separates import package from from pacakage import module and tides up the spaces between them. However, this is not enforced by PEP8 guidelines.

Projects should be configured to block merging on pull requests that do not conform to these standards.


Writing tests is strongly encouraged.

  • We write our tests in the tests folders. Files usually follow the test_*.py (pattern for unittest discovery)[].
  • After a tests have been written, we use the python3 -m unittest discover --start-directory tests to run them.
  • Once the tests are run successfully, you can check the coverage report by running coverage report -m to check that you have passed the minimum required level to avoid failing CI tests.

Please write tests for any new code if at all possible, and any efforts to improve test coverage on any project would be greatly appreciated.


You should document your functions with docstrings in accordance with PEP 257.