Using Granite with Python

py-elementary.py

import gi

gi.require_version("Gtk", "3.0")
gi.require_version("Granite", "1.0")
from gi.repository import Gtk
from gi.repository import Granite


class MyWindow(Gtk.Window):
    def __init__(self):
        Gtk.Window.__init__(self, title="Hello World")

        self.gtk_settings = Gtk.Settings.get_default()
        self.granite_settings = Granite.Settings.get_default()

        self.set_colour_scheme()
        self.granite_settings.connect("notify::prefers-color-scheme", self.set_colour_scheme)

    def set_colour_scheme(self, *args, **kwargs):
        self.gtk_settings.props.gtk_application_prefer_dark_theme = (
            self.granite_settings.props.prefers_color_scheme == Granite.SettingsColorScheme.DARK
        )


win = MyWindow()
win.connect("destroy", Gtk.main_quit)
win.show_all()
Gtk.main()