python-dbus-next

The next great DBus library for Python.

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python-dbus-next is a Python library for DBus that aims to be a fully featured high level library primarily geared towards integration of applications into Linux desktop and mobile environments.

Desktop application developers can use this library for integrating their applications into desktop environments by implementing common DBus standard interfaces or creating custom plugin interfaces.

Desktop users can use this library to create their own scripts and utilities to interact with those interfaces for customization of their desktop environment.

python-dbus-next plans to improve over other DBus libraries for Python in the following ways:

• Zero dependencies and pure Python 3.
• Support for multiple IO backends including asyncio and the GLib main loop.
• Nonblocking IO suitable for GUI development.
• Target the latest language features of Python for beautiful services and clients.
• Complete implementation of the DBus type system without ever guessing types.
• Integration tests for all features of the library.
• Completely documented public API.

Installing

This library is available on PyPi as dbus-next.

pip3 install dbus-next

The Client Interface

To use a service on the bus, the library constructs a proxy object you can use to call methods, get and set properties, and listen to signals.

For more information, see the overview for the high-level client.

This example connects to a media player and controls it with the MPRIS DBus interface.

fromdbus_next.aioimportMessageBusimportasyncioloop=asyncio.get_event_loop()
asyncdefmain():
bus=awaitMessageBus().connect()
# the introspection xml would normally be included in your project, but# this is convenient for developmentintrospection=awaitbus.introspect('org.mpris.MediaPlayer2.vlc', '/org/mpris/MediaPlayer2')
obj=bus.get_proxy_object('org.mpris.MediaPlayer2.vlc', '/org/mpris/MediaPlayer2', introspection)
player=obj.get_interface('org.mpris.MediaPlayer2.Player')
properties=obj.get_interface('org.freedesktop.DBus.Properties')
# call methods on the interface (this causes the media player to play)awaitplayer.call_play()
volume=awaitplayer.get_volume()
print(f'current volume: {volume}, setting to 0.5')
awaitplayer.set_volume(0.5)
# listen to signalsdefon_properties_changed(interface_name, changed_properties, invalidated_properties):
forchanged, variantinchanged_properties.items():
print(f'property changed: {changed} - {variant.value}')
properties.on_properties_changed(on_properties_changed)
awaitloop.create_future()
loop.run_until_complete(main())

The Service Interface

To define a service on the bus, use the ServiceInterface class and decorate class methods to specify DBus methods, properties, and signals with their type signatures.

For more information, see the overview for the high-level service.

fromdbus_next.serviceimportServiceInterface, method, dbus_property, signal, Variantfromdbus_next.aioimportMessageBusimportasyncioclassExampleInterface(ServiceInterface):
def__init__(self, name):
super().__init__(name)
self._string_prop='kevin'@method()defEcho(self, what: 's') ->'s':
returnwhat@method()defGetVariantDict() ->'a{sv}':
return {
'foo': Variant('s', 'bar'),
'bat': Variant('x', -55),
'a_list': Variant('as', ['hello', 'world'])
}
@dbus_property()defstring_prop(self) ->'s':
returnself._string_prop@string_prop.setterdefstring_prop_setter(self, val: 's'):
self._string_prop=val@signal()defsignal_simple(self) ->'s':
return'hello'asyncdefmain():
bus=awaitMessageBus().connect()
interface=ExampleInterface('test.interface')
bus.export('/test/path', interface)
# now that we are ready to handle requests, we can request name from D-Busawaitbus.request_name('test.name')
# wait indefinitelyawaitasyncio.get_event_loop().create_future()
asyncio.get_event_loop().run_until_complete(main())

The Low-Level Interface

The low-level interface works with DBus messages directly.

For more information, see the overview for the low-level interface.

fromdbus_next.messageimportMessage, MessageTypefromdbus_next.aioimportMessageBusimportasyncioimportjsonloop=asyncio.get_event_loop()
asyncdefmain():
bus=awaitMessageBus().connect()
reply=awaitbus.call(
Message(destination='org.freedesktop.DBus',
path='/org/freedesktop/DBus',
interface='org.freedesktop.DBus',
member='ListNames'))
ifreply.message_type==MessageType.ERROR:
raiseException(reply.body[0])
print(json.dumps(reply.body[0], indent=2))
loop.run_until_complete(main())

Projects that use python-dbus-next

• The Playerctl test suite
• i3-dstatus

Contributing

Contributions are welcome. Development happens on Github.

Before you commit, run make to run the linter, code formatter, and the test suite.

Copyright

You can use this code under an MIT license (see LICENSE).

© 2019, Tony Crisci