X-Git-Url: http://git.kaliko.me/?p=python-musicpd.git;a=blobdiff_plain;f=doc%2Fsource%2Fuse.rst;h=86c3e724416db7ef13eb3cd7cfbbf5e22c8419c8;hp=d8e46e7e7c216143d980d72bd4f3b3628c428683;hb=80fdad9f2cad5b3759351ab38bf32cad863cd3cb;hpb=e4003597f43ccb041f81827b56c082cf5554098d diff --git a/doc/source/use.rst b/doc/source/use.rst index d8e46e7..86c3e72 100644 --- a/doc/source/use.rst +++ b/doc/source/use.rst @@ -1,6 +1,12 @@ +.. SPDX-FileCopyrightText: 2018-2021 kaliko +.. SPDX-License-Identifier: LGPL-3.0-or-later + Using the client library ========================= +Introduction +------------ + The client library can be used as follows: .. code-block:: python @@ -11,14 +17,62 @@ The client library can be used as follows: # fallback to localhost:6600 # connect support host/port argument as well print(client.mpd_version) # print the mpd protocol version - print(client.cmd('one', 2)) # print result of the command "cmd one 2" + print(client.cmd('foo', 42)) # print result of the request "cmd foo 42" + # (nb. for actual command, see link to the protocol below) client.disconnect() # disconnect from the server -For a list of supported commands, their arguments (as MPD currently understands +In the example above `cmd` in not an actual MPD command, for a list of +supported commands, their arguments (as MPD currently understands them), and the functions used to parse their responses see :ref:`commands`. See the `MPD protocol documentation`_ for more details. +.. _environment_variables: + +Environment variables +--------------------- + +The client honors the following environment variables: + + * ``MPD_HOST`` MPD host (:abbr:`FQDN (fully qualified domain name)`, 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, ie with :abbr:`FQDN (fully qualified domain name)` defined host + * ``MPD_TIMEOUT`` timeout for connecting to MPD and waiting for MPD’s response in seconds + * ``XDG_RUNTIME_DIR`` path to look for potential socket: ``${XDG_RUNTIME_DIR}/mpd/socket`` + +.. _default_settings: + +Default settings +---------------- + + * If ``MPD_HOST`` is not set, then look for a socket in ``${XDG_RUNTIME_DIR}/mpd/socket`` + * If there is no socket use ``localhost`` + * If ``MPD_PORT`` is not set, then use ``6600`` + * If ``MPD_TIMEOUT`` is not set, then uses :py:obj:`musicpd.CONNECTION_TIMEOUT` + + +Context manager +--------------- + +Calling MPDClient in a context manager :py:obj:`musicpd.MPDClient.connect` is +transparently called with :ref:`default setting` (use +:ref:`environment variables` to override defaults). +Leaving the context manager :py:obj:`musicpd.MPDClient.disconnect` is called. + +.. code-block:: python + + 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()` : @@ -29,6 +83,9 @@ Command lists are also supported using `command_list_ok_begin()` and client.status() # insert the status command into the list results = client.command_list_end() # results will be a list with the results +Ranges +------ + Provide a 2-tuple as argument for command supporting ranges (cf. `MPD protocol documentation`_ for more details). Possible ranges are: "START:END", "START:" and ":" : @@ -52,6 +109,8 @@ as a single colon as argument (i.e. sending just ":"): Empty start in range (i.e. ":END") are not possible and will raise a CommandError. +Iterators +---------- Commands may also return iterators instead of lists if `iterate` is set to `True`: @@ -62,8 +121,11 @@ Commands may also return iterators instead of lists if `iterate` is set to for song in client.playlistinfo(): print song['file'] +Idle prefixed commands +---------------------- + Each command have a *send\_* and a *fetch\_* variant, which allows to -send a MPD command and then fetch the result later. +send a MPD command and then fetch the result later (non-blocking call). This is useful for the idle command: .. code-block:: python @@ -84,5 +146,127 @@ This is useful for the idle command: >>> gobject.io_add_watch(client, gobject.IO_IN, callback) >>> gobject.MainLoop().run() +See also use of :ref:`socket timeout` with idle command. + +Fetching binary content (cover art) +----------------------------------- + +Fetching album covers is possible with albumart, here is an example: + +.. code-block:: python + + >>> 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 `CommandError` is raised if the album does not expose a cover. + +You can also use `readpicture` command to fetch embedded picture: + +.. code-block:: python + + >>> 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: + +Socket timeout +-------------- + +.. note:: + When the timeout is reached it raises a :py:obj:`socket.timeout` exception. An :py:obj:`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 +:py:obj:`musicpd.CONNECTION_TIMEOUT` at module level and +:py:obj:`musicpd.MPDClient.mpd_timeout` in MPDClient instances . However it +is possible to set socket timeout for all command setting +:py:obj:`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``: + +.. code-block:: python + + 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). + .. _MPD protocol documentation: http://www.musicpd.org/doc/protocol/ +.. vim: spell spelllang=en