X-Git-Url: https://git.kaliko.me/?a=blobdiff_plain;f=doc%2Fsource%2Fuse.rst;h=119de2dfc975cc69f4762bba5ffa347c856e470a;hb=43efcdd63b071ef5a5224fec37ebf298cfacd0f9;hp=fdc13178306852e2d1cf48e97470018cff65a75c;hpb=966e3a848b9d545530cc7c7a78c5185c69183b22;p=python-musicpd.git diff --git a/doc/source/use.rst b/doc/source/use.rst index fdc1317..119de2d 100644 --- a/doc/source/use.rst +++ b/doc/source/use.rst @@ -1,61 +1,174 @@ +.. SPDX-FileCopyrightText: 2018-2023 kaliko +.. SPDX-License-Identifier: LGPL-3.0-or-later + Using the client library ========================= -The client library can be used as follows:: +Introduction +------------ + +The client library can be used as follows: + +.. code-block:: python 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 version - print client.cmd('one', 2) # print result of the command "cmd one 2" - client.close() # send the close command + print(client.mpd_version) # print the MPD protocol version + client.setvol('42') # sets the volume client.disconnect() # disconnect from the server -A list of supported commands, their arguments (as MPD currently understands -them), and the functions used to parse their responses can be found in -`doc/commands.txt`. See the `MPD protocol documentation`_ for more -details. +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 :py:class:`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. + +:py:class:`musicpd.MPDClient` methods returns different kinds of objects depending on the command. Could be :py:obj:`None`, a single object as a :py:obj:`str` or a :py:obj:`dict`, a list of :py:obj:`dict`. + +For more about the protocol and MPD commands see the `MPD protocol +documentation`_. + +For a list of currently supported commands in this python module see +:ref:`commands`. + +.. _environment_variables: + +Environment variables +--------------------- + +:py:class:`musicpd.MPDClient` honors the following environment variables: + +.. envvar:: MPD_HOST + + MPD host (:abbr:`FQDN (fully qualified domain name)`, IP, socket path or abstract socket) and password. + + | To define a **password** set :envvar:`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*" + +.. envvar:: MPD_PORT + + MPD port, relevant for TCP socket only + +.. envvar:: MPD_TIMEOUT + + socket timeout when connecting to MPD and waiting for MPD’s response (in seconds) + +.. envvar:: XDG_RUNTIME_DIR + + path to look for potential socket + +.. _default_settings: + +Default settings +---------------- + +Default host: + * use :envvar:`MPD_HOST` environment variable if set, extract password if present, + * else looks for an existing file in :envvar:`${XDG_RUNTIME_DIR:-/run/}/mpd/socket` + * else set host to ``localhost`` + +Default port: + * use :envvar:`MPD_PORT` environment variable is set + * else use ``6600`` + +Default timeout: + * use :envvar:`MPD_TIMEOUT` is set + * else use :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()` :: +`command_list_end()` : + +.. code-block:: python 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 -Provide a 2-tuple as argument for command supporting ranges (cf. `MPD protocol documentation`_ for more details). -Possible ranges are: "START:END", "START:" and ":" :: +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 :py:obj:`tuple` as `(START,END)`. The module is then ensuring the format is correct and raises an :py:obj:`musicpd.CommandError` exception otherwise. Empty start or end can be specified as en empty string ``''`` or :py:obj:`None`. + +.. code-block:: python # An intelligent clear # clears played track in the queue, currentsong included pos = client.currentsong().get('pos', 0) - # the 2-tuple range object accepts str, no need to convert to int + # 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 ":"):: +A notable case is the *rangeid* command allowing an empty range specified +as a single colon as argument (i.e. sending just ``":"``): + +.. code-block:: python # 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. +Remember the of the tuple is optional, range can still be specified as single string ``"START:END"``. + +Iterators +---------- Commands may also return iterators instead of lists if `iterate` is set to -`True`:: +`True`: + +.. code-block:: python client.iterate = True 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. -This is useful for the idle command:: +send a MPD command and then fetch the result later (non-blocking call). +This is useful for the idle command: + +.. code-block:: python >>> client.send_idle() # do something else or use function like select() @@ -73,5 +186,128 @@ 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/ +.. _snake case: https://en.wikipedia.org/wiki/Snake_case +.. vim: spell spelllang=en