Python coding guidelines¶
We ask that all Python contributions adhere to the PEP8 style guide, apart from the restriction on line length (E501) and some minor docstring-related issues.
The list of PEP8 violations to ignore is in the
tox.ini file, under the
You might want to configure the flake8 linter in your editor/IDE to use the configuration in this file.
In addition, import lines should be sorted according to isort 4.2.5 rules. If you have installed Wagtail’s testing dependencies (
pip install -e .[testing]), you can check your code by running
Python 2 and 3 compatibility¶
All contributions should support Python 2 and 3 and we recommend using the six compatibility library (use the version bundled with Django,
Wagtail is written to be compatible with multiple versions of Django. Sometimes, this requires running one piece of code for recent version of Django, and another piece of code for older versions of Django. In these cases, always check which version of Django is being used by inspecting
import django if django.VERSION >= (1, 9): # Use new attribute related_field = field.rel else: # Use old, deprecated attribute related_field = field.related
Always compare against the version using greater-or-equals (
>=), so that code for newer versions of Django is first.
Do not use a
try ... except when seeing if an object has an attribute or method introduced in a newer versions of Django, as it does not clearly express why the
try ... except is used. An explicit check against the Django version makes the intention of the code very clear.
# Do not do this try: related_field = field.rel except AttributeError: related_field = field.related
If the code needs to use something that changed in a version of Django many times, consider making a function that encapsulates the check:
import django def related_field(field): if django.VERSION >= (1, 9): return field.rel else: return field.related
If a new function has been introduced by Django that you think would be very useful for Wagtail, but is not available in older versions of Django that Wagtail supports, that function can be copied over in to Wagtail. If the user is running a new version of Django that has the function, the function should be imported from Django. Otherwise, the version bundled with Wagtail should be used. A link to the Django source code where this function was taken from should be included:
import django if django.VERSION >= (1, 9): from django.core.validators import validate_unicode_slug else: # Taken from https://github.com/django/django/blob/1.9/django/core/validators.py#L230 def validate_unicode_slug(value): # Code left as an exercise to the reader pass
Wagtail has a suite of tests, which we are committed to improving and expanding. See Testing.
We run continuous integration at travis-ci.org/wagtail/wagtail to ensure that no commits or pull requests introduce test failures. If your contributions add functionality to Wagtail, please include the additional tests to cover it; if your contributions alter existing functionality, please update the relevant tests accordingly.