Coding Style Guide

The code must be easy to understand, so it should look consistent.

When entering the development environment, a git pre-commit hook is set up on your local repo. When you create a commit, the hook runs the pre-commit tool which:

• performs some lightweight checks

• runs flake8 to check the code style

• runs pylint in the sandbox to check for all kinds of errors.

We rely on the Python Style Guide PEP-8

Line length

When deciding whether or not you should split your line when it exceeds 79 characters, ask yourself: "Does it truly improve legibility?"

What this translates to is:

• Avoid having very long lines.

• When the contents only slightly exceeds the 80 chars limit, consider keeping it on one line. Otherwise it just hurts legibility and gives a weird "shape" to the code.

Names

The function names, method names and other class attributes should be small_caps_with_underscore. For example:

def some_function():
    return ""

class MyClass:

    def a_really_important_method(self):
        self.do_something()

    @property
    def water_level(self):
        """The level of the water in meters."""
        return self.__water_level

To illustrate how private a method or other class field is, prepend one or two underscores:

  class MyClass:

     def public_method(self):
         ...

     def _protected_method(self):
         ...

     def __private_method(self):
         ...

Unused arguments in methods should be prefixed with unused_. The most common place where this would happen is in callbacks from gobject signals. For example, below we don't use the second argument, but we do use pad.

     def __pad_added_cb(self, unused_element, pad):
        self.do_something_with(pad)

The name of a callback method should:

• be prepended with two underscores since it's private
• be appended with cb

  class MyClass:

     def some_method(self):
         self.someobject.connect("event", self.__some_object_event_cb)

     def __some_object_event_cb(self, object, arg):
         print "our callback was called"

Docstrings

We follow the Google Python Style Guide for docstrings.