Quick demo which pops a simple notification on the screen using DBus.

dbus-notify.py

#!/usr/bin/python3

from pydbus import SessionBus

bus = SessionBus()

# Create an object that will proxy for a particular remote object.
remote_object = bus.get(
    'org.gnome.Shell.Notifications', # Bus name
    '/org/freedesktop/Notifications' # Object path
)

remote_object.Notify(
    '',                 # App name
    0,                  # Replace id
    'im.received',      # Icon
    'Python script',    # Summary
                        # Body
    'This is a message from Python land!',
    [],
    [],
    0
)