The pygal code tries to respect the pep8 please keep that in mind when writing code for pygal. (The code style is checked along with the unit tests, see next paragraph).
Before submiting a pull request, please check that all tests still pass.
To do this install
py.test and them run
py.test in the root of your pygal clone:
[dev@dev pygal/]$ py.test --flake8
Even better if you have several python versions installed you can run