Simple libnotify implementation using only plain dbus-send. Can close created notification.

simple_notify.py

import sys
from subprocess import Popen, PIPE

def notify(title, body=None, timeout=-1, appname='simple-notify'):
    cmd = [
        'dbus-send',
        '--type=method_call',
        '--print-reply=literal',
        '--dest=org.freedesktop.Notifications',
        '/org/freedesktop/Notifications',
        'org.freedesktop.Notifications.Notify',
        'string:{}'.format(appname),
        'uint32:0',
        'string:""',
        'string:{}'.format(title),
        'string:{}'.format(body),
        'array:string:""',
        'dict:string:string:"",""',
        'int32:{}'.format(timeout),
    ]

    out, err = Popen(cmd, stdout=PIPE, stderr=PIPE).communicate()
    if err:
        raise Exception(err)

    return int(out.strip().split()[1])

def close(nid):
    cmd = [
        'dbus-send',
        '--type=method_call',
        '--dest=org.freedesktop.Notifications',
        '/org/freedesktop/Notifications',
        'org.freedesktop.Notifications.CloseNotification',
        'int32:{}'.format(nid),
    ]

    out, err = Popen(cmd, stdout=PIPE, stderr=PIPE).communicate()
    if err:
        raise Exception(err)

if __name__ == '__main__':
    if sys.argv[1] == 'close':
        close(sys.argv[2])
    else:
        print notify(*sys.argv[1:4])

This doesn't work. 🙁 It gives me this error:

Exception: Error org.freedesktop.DBus.Error.InvalidArgs: Type of message, '(susssasa{ss}i)', does not match expected type '(susssasa{sv}i)'

As used here, the values in the dict are strings, but that doesn't match the desktop notifications spec, which says that the hints dict should have variant values.
Sadly, it seems dbus-send doesn't allow specifying a dict with variant values, so there's no way to use dbus-send to create freedesktop notifications.

You can use gdbus call, though