Using the client library

Introduction

The client library can be used as follows:

client = musicpd.MPDClient()       # create client object
client.connect()                   # use MPD_HOST/MPD_PORT if set else
                                   #   test ${XDG_RUNTIME_DIR}/mpd/socket for existence
                                   #   fallback to localhost:6600
                                   # connect support host/port argument as well
print(client.mpd_version)          # print the MPD protocol version
client.setvol('42')                # sets the volume
client.disconnect()                # disconnect from the server

The MPD command protocol exchanges line-based text records. The client emits a command with optional arguments. In the example above the client sends a setvol command with the string argument 42.

MPD commands are exposed as musicpd.MPDClient methods. Methods arguments are python strings. Some commands are composed of more than one word (ie “tagtypes [disable|enable|all]”), for these use a snake case style to access the method. Then “tagtypes enable” command is called with “tagtypes_enable”.

Remember MPD protocol is text based, then all MPD command arguments are UTF-8 strings. In the example above, an integer can be used as argument for the setvol command, but it is then evaluated as a string when the command is written to the socket. To avoid confusion use regular string instead of relying on object string representation.

musicpd.MPDClient methods returns different kinds of objects depending on the command. Could be None, a single object as a str, a list, a dict or a list of dict. See commands exposed in the module for more about returned type.

Then musicpd.MPDClient methods signatures are not hard coded within this module since the protocol is handled on the server side. Please refer to the protocol and MPD commands in MPD protocol documentation to learn how to call commands and what kind of arguments they expect.

Some examples are provided for the most common cases, see Examples.

For a list of currently supported commands in this python module see Available commands.

Environment variables

musicpd.MPDClient honors the following environment variables:

MPD_HOST

MPD host (FQDN, IP, socket path or abstract socket) and password.

To define a password set MPD_HOST to “password@host” (password only “password@”)
For abstract socket use “@” as prefix : “@socket” and then with a password “pass@@socket
Regular unix socket are set with an absolute path: “/run/mpd/socket
MPD_PORT

MPD port, relevant for TCP socket only

MPD_TIMEOUT

socket timeout when connecting to MPD and waiting for MPD’s response (in seconds)

XDG_RUNTIME_DIR

path to look for potential socket

Default settings

Default host:
  • use MPD_HOST environment variable if set, extract password if present,

  • else use XDG_RUNTIME_DIR to looks for an existing file in ${XDG_RUNTIME_DIR}/mpd/socket, XDG_RUNTIME_DIR defaults to /run if not set.

  • else set host to localhost

Default port:
  • use MPD_PORT environment variable if set

  • else use 6600

Default timeout:

Context manager

Calling MPDClient in a context manager musicpd.MPDClient.connect is transparently called with default setting (use environment variables to override defaults). Leaving the context manager musicpd.MPDClient.disconnect is called.

import os
os.environ['MPD_HOST'] = 'mpdhost'
with MPDClient() as c:
    c.status()
    c.next()

Command lists

Command lists are also supported using command_list_ok_begin() and command_list_end() :

client.command_list_ok_begin()       # start a command list
client.update()                      # insert the update command into the list
client.status()                      # insert the status command into the list
results = client.command_list_end()  # results will be a list with the results

Ranges

Some commands (e.g. delete) allow specifying a range in the form “START:END” (cf. MPD protocol documentation for more details).

Possible ranges are: “START:END”, “START:” and “:” :

Instead of giving the plain string as “START:END”, you can provide a tuple as (START,END). The module is then ensuring the format is correct and raises an musicpd.CommandError exception otherwise. Empty start or end can be specified as en empty string '' or None.

# An intelligent clear
# clears played track in the queue, currentsong included
pos = client.currentsong().get('pos', 0)
# the range object accepts str, no need to convert to int
client.delete((0, pos))
# missing end interpreted as highest value possible, pay attention still need a tuple.
client.delete((pos,))  # purge queue from current to the end

A notable case is the rangeid command allowing an empty range specified as a single colon as argument (i.e. sending just ":"):

# sending "rangeid :" to clear the range, play everything
client.rangeid(())  # send an empty tuple

Empty start in range (i.e. “:END”) are not possible and will raise a CommandError.

Note

Remember the use of a tuple is optional. Range can still be specified as a plain string "START:END".

Iterators

Commands may also return iterators instead of lists if iterate is set to True:

client.iterate = True
for song in client.playlistinfo():
    print song['file']

Idle prefixed commands

Each command have a send_<CMD> and a fetch_<CMD> variant, which allows to send a MPD command and then fetch the result later (non-blocking call). This is useful for the idle command:

>>> client.send_idle()
# do something else or use function like select()
# http://docs.python.org/howto/sockets.html#non-blocking-sockets
# ex. select([client], [], [])
>>> events = client.fetch_idle()

# more complex use for example, with glib/gobject:
>>> def callback(source, condition):
>>>    changes = client.fetch_idle()
>>>    print changes
>>>    return False  # removes the IO watcher

>>> client.send_idle()
>>> gobject.io_add_watch(client, gobject.IO_IN, callback)
>>> gobject.MainLoop().run()

See also use of socket timeout with idle command.

Fetching binary content (cover art)

Fetching album covers is possible with albumart, here is an example:

>>> cli = musicpd.MPDClient()
>>> cli.connect()
>>> track = "Steve Reich/1978-Music for 18 Musicians"
>>> aart = cli.albumart(track, 0)
>>> received = int(aart.get('binary'))
>>> size = int(aart.get('size'))
>>> with open('/tmp/cover', 'wb') as cover:
>>>     # aart = {'size': 42, 'binary': 2051, data: bytes(...)}
>>>     cover.write(aart.get('data'))
>>>     while received < size:
>>>         aart = cli.albumart(track, received)
>>>         cover.write(aart.get('data'))
>>>         received += int(aart.get('binary'))
>>>     if received != size:
>>>         print('something went wrong', file=sys.stderr)
>>> cli.disconnect()

A musicpd.CommandError is raised if the album does not expose a cover.

You can also use readpicture command to fetch embedded picture:

>>> cli = musicpd.MPDClient()
>>> cli.connect()
>>> track = 'muse/Amon Tobin/2011-ISAM/01-Amon Tobin - Journeyman.mp3'
>>> rpict = cli.readpicture(track, 0)
>>> if not rpict:
>>>     print('No embedded picture found', file=sys.stderr)
>>>     sys.exit(1)
>>> size = int(rpict['size'])
>>> done = int(rpict['binary'])
>>> with open('/tmp/cover', 'wb') as cover:
>>>     cover.write(rpict['data'])
>>>     while size > done:
>>>         rpict = cli.readpicture(track, done)
>>>         done += int(rpict['binary'])
>>>         print(f'writing {rpict["binary"]}, done {100*done/size:03.0f}%')
>>>         cover.write(rpict['data'])
>>> cli.disconnect()

Refer to MPD protocol documentation for the meaning of binary, size and data.

Socket timeout

Note

When the timeout is reached it raises a socket.timeout exception. An OSError subclass.

A timeout is used for the initial MPD connection (connect command), then the socket is put in blocking mode with no timeout. Its value is set in musicpd.CONNECTION_TIMEOUT at module level and musicpd.MPDClient.mpd_timeout in MPDClient instances . However it is possible to set socket timeout for all command setting musicpd.MPDClient.socket_timeout attribute to a value in second.

Having socket_timeout enabled can help to detect “half-open connection”. For instance loosing connectivity without the server explicitly closing the connection (switching network interface ethernet/wifi, router down, etc…).

Nota bene: with socket_timeout enabled each command sent to MPD might timeout. A couple of seconds should be enough for commands to complete except for the special case of idle command which by definition “ waits until there is a noteworthy change in one or more of MPD’s subsystems.” (cf. MPD protocol documentation).

Here is a solution to use idle command with socket_timeout:

import musicpd
import select
import socket

cli = musicpd.MPDClient()
try:
    cli.socket_timeout = 10  # seconds
    select_timeout = 5 # second
    cli.connect()
    while True:
        cli.send_idle()  # use send_ API to avoid blocking on read
        _read, _, _ = select.select([cli], [], [], select_timeout)
        if _read:  # tries to read response
            ret = cli.fetch_idle()
            print(', '.join(ret))  # Do something
        else: # cancels idle
            cli.noidle()
except socket.timeout as err:
    print(f'{err} (timeout {cli.socket_timeout})')
except (OSError, musicpd.MPDError) as err:
    print(f'{err!r}')
    if cli._sock is not None:
        cli.disconnect()
except KeyboardInterrupt:
    pass

Some explanations:

  • First launch a non blocking idle command. This call do not wait for a response to avoid socket timeout waiting for an MPD event.

  • select waits for something to read on the socket (the idle response in this case), returns after select_timeout seconds anyway.

  • In case there is something to read read it using fetch_idle

  • Nothing to read, cancel idle with noidle

All three commands in the while loop (send_idle, fetch_idle, noidle) are not triggering a socket timeout unless the connection is actually lost (actually it could also be that MPD took too much time to answer, but MPD taking more than a couple of seconds for these commands should never occur).

Exceptions

The connect method raises ConnectionError only (an MPDError exception) but then, calling other MPD commands, the module can raise MPDError or an OSError depending on the error and where it occurs.

Then using musicpd module both musicpd.MPDError and OSError exceptions families are expected, see examples for a way to deal with this.