Refactored Tornado routes for native pub/sub support.

The Redis pub/sub mechanism is now a native feature for Tornado routes
through the `PubSubMixin`.

(Plus, lint/black chore for the sound plugin)

platypush/backend/http/__init__.py

@@ -17,11 +17,10 @@ from tornado.web import Application, FallbackHandler
 from platypush.backend import Backend
 from platypush.backend.http.app import application
 from platypush.backend.http.app.utils import get_streaming_routes, get_ws_routes
-from platypush.backend.http.app.ws.events import events_redis_topic
+from platypush.backend.http.app.ws.events import WSEventProxy
 
 from platypush.bus.redis import RedisBus
 from platypush.config import Config
-from platypush.utils import get_redis
 
 
 class HttpBackend(Backend):
@@ -286,7 +285,7 @@ class HttpBackend(Backend):
 
     def notify_web_clients(self, event):
         """Notify all the connected web clients (over websocket) of a new event"""
-        get_redis().publish(events_redis_topic, str(event))
+        WSEventProxy.publish(event)  # noqa: E1120
 
     def _get_secret_key(self, _create=False):
         if _create:

platypush/backend/http/app/mixins/__init__.py

@@ -0,0 +1,158 @@
+from contextlib import contextmanager
+from dataclasses import dataclass
+import json
+import logging
+from multiprocessing import RLock
+from typing import Generator, Iterable, Optional, Set, Union
+
+from redis import ConnectionError as RedisConnectionError
+from redis.client import PubSub
+
+from platypush.config import Config
+from platypush.message import Message as AppMessage
+from platypush.utils import get_redis
+
+logger = logging.getLogger(__name__)
+
+MessageType = Union[AppMessage, bytes, str, dict, list, set, tuple]
+"""Types of supported messages on Redis/websocket channels."""
+
+
+@dataclass
+class Message:
+    """
+    A wrapper for a message received on a Redis subscription.
+    """
+
+    data: bytes
+    """The data received in the message."""
+    channel: str
+    """The channel the message was received on."""
+
+
+class PubSubMixin:
+    """
+    A mixin for Tornado route handlers that support pub/sub mechanisms.
+    """
+
+    def __init__(self, *_, subscriptions: Optional[Iterable[str]] = None, **__):
+        self._pubsub: Optional[PubSub] = None
+        """Pub/sub proxy."""
+        self._subscriptions: Set[str] = set(subscriptions or [])
+        """Set of current channel subscriptions."""
+        self._pubsub_lock = RLock()
+        """
+        Subscriptions lock. It ensures that the list of subscriptions is
+        manipulated by one thread or process at the time.
+        """
+
+        self.subscribe(*self._subscriptions)
+
+    @property
+    @contextmanager
+    def pubsub(self):
+        """
+        Pub/sub proxy lazy property with context manager.
+        """
+        with self._pubsub_lock:
+            # Lazy initialization for the pub/sub object.
+            if self._pubsub is None:
+                self._pubsub = get_redis().pubsub()
+
+        # Yield the pub/sub object (context manager pattern).
+        yield self._pubsub
+
+        with self._pubsub_lock:
+            # Close and free the pub/sub object if it has no active subscriptions.
+            if self._pubsub is not None and len(self._subscriptions) == 0:
+                self._pubsub.close()
+                self._pubsub = None
+
+    @staticmethod
+    def _serialize(data: MessageType) -> bytes:
+        """
+        Serialize a message as bytes before delivering it to either a Redis or websocket channel.
+        """
+        if isinstance(data, AppMessage):
+            data = str(data)
+        if isinstance(data, (list, tuple, set)):
+            data = list(data)
+        if isinstance(data, (list, dict)):
+            data = json.dumps(data, cls=AppMessage.Encoder)
+        if isinstance(data, str):
+            data = data.encode('utf-8')
+
+        return data
+
+    @classmethod
+    def publish(cls, data: MessageType, *channels: str) -> None:
+        """
+        Publish data on one or more Redis channels.
+        """
+        for channel in channels:
+            get_redis().publish(channel, cls._serialize(data))
+
+    def subscribe(self, *channels: str) -> None:
+        """
+        Subscribe to a set of Redis channels.
+        """
+        with self.pubsub as pubsub:
+            for channel in channels:
+                pubsub.subscribe(channel)
+                self._subscriptions.add(channel)
+
+    def unsubscribe(self, *channels: str) -> None:
+        """
+        Unsubscribe from a set of Redis channels.
+        """
+        with self.pubsub as pubsub:
+            for channel in channels:
+                if channel in self._subscriptions:
+                    pubsub.unsubscribe(channel)
+                    self._subscriptions.remove(channel)
+
+    def listen(self) -> Generator[Message, None, None]:
+        """
+        Listens for pub/sub messages and yields them.
+        """
+        try:
+            with self.pubsub as pubsub:
+                for msg in pubsub.listen():
+                    channel = msg.get('channel', b'').decode()
+                    if msg.get('type') != 'message' or not (
+                        channel and channel in self._subscriptions
+                    ):
+                        continue
+
+                    yield Message(data=msg.get('data', b''), channel=channel)
+        except (AttributeError, RedisConnectionError):
+            return
+
+    def _pubsub_close(self):
+        """
+        Closes the pub/sub object.
+        """
+        with self._pubsub_lock:
+            if self._pubsub is not None:
+                try:
+                    self._pubsub.close()
+                except Exception as e:
+                    logger.debug('Error on pubsub close: %s', e)
+                finally:
+                    self._pubsub = None
+
+    def on_close(self):
+        """
+        Extensible close handler that closes the pub/sub object.
+        """
+        self._pubsub_close()
+
+    @staticmethod
+    def get_channel(channel: str) -> str:
+        """
+        Utility method that returns the prefixed Redis channel for a certain subscription name.
+        """
+        return f'_platypush/{Config.get("device_id")}/{channel}'  # type: ignore
+
+
+# vim:sw=4:ts=4:et:

platypush/backend/http/app/streaming/_base.py

@@ -9,18 +9,23 @@ from tornado.web import RequestHandler, stream_request_body
 
 from platypush.backend.http.app.utils.auth import AuthStatus, get_auth_status
 
+from ..mixins import PubSubMixin
+
 logger = getLogger(__name__)
 
 
 @stream_request_body
-class StreamingRoute(RequestHandler, ABC):
+class StreamingRoute(RequestHandler, PubSubMixin, ABC):
     """
     Base class for Tornado streaming routes.
     """
 
     @override
     def prepare(self):
-        # Perform authentication
+        """
+        Request preparation logic. It performs user authentication if
+        ``auth_required`` returns True, and it can be extended/overridden.
+        """
         if self.auth_required:
             auth_status = get_auth_status(self.request)
             if auth_status != AuthStatus.OK:
@@ -33,18 +38,28 @@ class StreamingRoute(RequestHandler, ABC):
 
     @override
     def write_error(self, status_code: int, error: Optional[str] = None, **_):
+        """
+        Make sure that errors are always returned in JSON format.
+        """
         self.set_header("Content-Type", "application/json")
         self.finish(
             json.dumps(
-                {"status": status_code, "error": error or responses[status_code]}
+                {"status": status_code, "error": error or responses.get(status_code)}
             )
         )
 
     @classmethod
     @abstractmethod
     def path(cls) -> str:
+        """
+        Path/URL pattern for this route.
+        """
         raise NotImplementedError()
 
     @property
-    def auth_required(self):
+    def auth_required(self) -> bool:
+        """
+        If set to True (default) then this route will require user
+        authentication and return 401 if authentication fails.
+        """
         return True

platypush/backend/http/app/streaming/plugins/camera.py

@@ -56,6 +56,8 @@ class CameraRoute(StreamingRoute):
                 camera.stream.ready.wait(timeout=timeout)
                 return camera.stream.frame
 
+        return None
+
     def _should_stop(self):
         if self._finished:
             return True

platypush/backend/http/app/ws/__init__.py

@@ -1,3 +1,3 @@
-from ._base import WSRoute, logger, pubsub_redis_topic
+from ._base import WSRoute, logger
 
-__all__ = ['WSRoute', 'logger', 'pubsub_redis_topic']
+__all__ = ['WSRoute', 'logger']

platypush/backend/http/app/ws/_base.py

@@ -1,37 +1,28 @@
-from abc import ABC, abstractclassmethod
-import json
+from abc import ABC, abstractmethod
 from logging import getLogger
-from threading import RLock, Thread
-from typing import Any, Generator, Iterable, Optional, Union
+from threading import Thread
 from typing_extensions import override
 
-from redis import ConnectionError as RedisConnectionError
 from tornado.ioloop import IOLoop
 from tornado.websocket import WebSocketHandler
 
 from platypush.backend.http.app.utils.auth import AuthStatus, get_auth_status
-from platypush.config import Config
-from platypush.message import Message
-from platypush.utils import get_redis
+
+from ..mixins import MessageType, PubSubMixin
 
 logger = getLogger(__name__)
 
 
-def pubsub_redis_topic(topic: str) -> str:
-    return f'_platypush/{Config.get("device_id")}/{topic}'  # type: ignore
-
-
-class WSRoute(WebSocketHandler, Thread, ABC):
+class WSRoute(WebSocketHandler, Thread, PubSubMixin, ABC):
     """
     Base class for Tornado websocket endpoints.
     """
 
-    def __init__(self, *args, redis_topics: Optional[Iterable[str]] = None, **kwargs):
-        super().__init__(*args, **kwargs)
-        self._redis_topics = set(redis_topics or [])
-        self._sub = get_redis().pubsub()
+    def __init__(self, *args, **kwargs):
+        WebSocketHandler.__init__(self, *args)
+        PubSubMixin.__init__(self, **kwargs)
+        Thread.__init__(self)
         self._io_loop = IOLoop.current()
-        self._sub_lock = RLock()
 
     @override
     def open(self, *_, **__):
@@ -51,10 +42,11 @@ class WSRoute(WebSocketHandler, Thread, ABC):
         pass
 
     @override
-    def on_message(self, message):  # type: ignore
-        pass
+    def on_message(self, message):
+        return message
 
-    @abstractclassmethod
+    @classmethod
+    @abstractmethod
     def app_name(cls) -> str:
         raise NotImplementedError()
 
@@ -66,55 +58,25 @@ class WSRoute(WebSocketHandler, Thread, ABC):
     def auth_required(self):
         return True
 
-    def subscribe(self, *topics: str) -> None:
-        with self._sub_lock:
-            for topic in topics:
-                self._sub.subscribe(topic)
-                self._redis_topics.add(topic)
-
-    def unsubscribe(self, *topics: str) -> None:
-        with self._sub_lock:
-            for topic in topics:
-                if topic in self._redis_topics:
-                    self._sub.unsubscribe(topic)
-                    self._redis_topics.remove(topic)
-
-    def listen(self) -> Generator[Any, None, None]:
-        try:
-            for msg in self._sub.listen():
-                if (
-                    msg.get('type') != 'message'
-                    and msg.get('channel').decode() not in self._redis_topics
-                ):
-                    continue
-
-                yield msg.get('data')
-        except (AttributeError, RedisConnectionError):
-            return
-
-    def send(self, msg: Union[str, bytes, dict, list, tuple, set]) -> None:
-        if isinstance(msg, (list, tuple, set)):
-            msg = list(msg)
-        if isinstance(msg, (list, dict)):
-            msg = json.dumps(msg, cls=Message.Encoder)
-
+    def send(self, msg: MessageType) -> None:
         self._io_loop.asyncio_loop.call_soon_threadsafe(  # type: ignore
-            self.write_message, msg
+            self.write_message, self._serialize(msg)
         )
 
     @override
     def run(self) -> None:
         super().run()
-        for topic in self._redis_topics:
-            self._sub.subscribe(topic)
+        self.subscribe(*self._subscriptions)
 
     @override
     def on_close(self):
-        topics = self._redis_topics.copy()
-        for topic in topics:
-            self.unsubscribe(topic)
+        super().on_close()
+        for channel in self._subscriptions.copy():
+            self.unsubscribe(channel)
+
+        if self._pubsub:
+            self._pubsub.close()
 
-        self._sub.close()
         logger.info(
             'Client %s disconnected from %s, reason=%s, message=%s',
             self.request.remote_ip,

platypush/backend/http/app/ws/events.py

@@ -1,12 +1,11 @@
 from typing_extensions import override
 
+from platypush.backend.http.app.mixins import MessageType
 from platypush.message.event import Event
 
-from . import WSRoute, logger, pubsub_redis_topic
+from . import WSRoute, logger
 from ..utils import send_message
 
-events_redis_topic = pubsub_redis_topic('events')
-
 
 class WSEventProxy(WSRoute):
     """
@@ -14,14 +13,23 @@ class WSEventProxy(WSRoute):
     """
 
     def __init__(self, *args, **kwargs):
-        super().__init__(*args, **kwargs)
-        self.subscribe(events_redis_topic)
+        super().__init__(*args, subscriptions=[self.events_channel], **kwargs)
 
     @classmethod
     @override
     def app_name(cls) -> str:
         return 'events'
 
+    @classmethod
+    @property
+    def events_channel(cls) -> str:
+        return cls.get_channel('events')
+
+    @override
+    @classmethod
+    def publish(cls, data: MessageType, *_) -> None:
+        super().publish(data, cls.events_channel)
+
     @override
     def on_message(self, message):
         try:
@@ -38,9 +46,9 @@ class WSEventProxy(WSRoute):
     def run(self) -> None:
         for msg in self.listen():
             try:
-                evt = Event.build(msg)
+                evt = Event.build(msg.data)
             except Exception as e:
                 logger.warning('Error parsing event: %s: %s', msg, e)
                 continue
 
-            self.send(str(evt))
+            self.send(evt)

platypush/plugins/camera/model/camera.py

@@ -5,7 +5,11 @@ from typing import Optional, Union, Tuple, Set
 
 import numpy as np
 
-from platypush.plugins.camera.model.writer import StreamWriter, VideoWriter, FileVideoWriter
+from platypush.plugins.camera.model.writer import (
+    StreamWriter,
+    VideoWriter,
+    FileVideoWriter,
+)
 from platypush.plugins.camera.model.writer.preview import PreviewWriter
 
 
@@ -32,7 +36,7 @@ class CameraInfo:
     stream_format: Optional[str] = None
     vertical_flip: bool = False
     warmup_frames: int = 0
-    warmup_seconds: float = 0.
+    warmup_seconds: float = 0.0
 
     def set(self, **kwargs):
         for k, v in kwargs.items():
@@ -97,10 +101,15 @@ class Camera:
         return writers
 
     def effective_resolution(self) -> Tuple[int, int]:
+        """
+        Calculates the effective resolution of the camera in pixels, taking
+        into account the base resolution, the scale and the rotation.
+        """
+        assert self.info.resolution, 'No base resolution specified'
         rot = (self.info.rotate or 0) * math.pi / 180
         sin = math.sin(rot)
         cos = math.cos(rot)
-        scale = np.array([[self.info.scale_x or 1., self.info.scale_y or 1.]])
+        scale = np.array([[self.info.scale_x or 1.0, self.info.scale_y or 1.0]])
         resolution = np.array([[self.info.resolution[0], self.info.resolution[1]]])
         rot_matrix = np.array([[sin, cos], [cos, sin]])
         resolution = (scale * abs(np.cross(rot_matrix, resolution)))[0]

platypush/plugins/sound/__init__.py

@@ -1,7 +1,3 @@
-"""
-.. moduleauthor:: Fabio Manganiello <blacklight86@gmail.com>
-"""
-
 import os
 import queue
 import stat
@@ -10,25 +6,28 @@ import time
 
 from enum import Enum
 from threading import Thread, Event, RLock
-
-from .core import Sound, Mix
+from typing import Optional
 
 from platypush.context import get_bus
-from platypush.message.event.sound import \
-    SoundRecordingStartedEvent, SoundRecordingStoppedEvent
+from platypush.message.event.sound import (
+    SoundRecordingStartedEvent,
+    SoundRecordingStoppedEvent,
+)
 
 from platypush.plugins import Plugin, action
 
+from .core import Sound, Mix
+
 
 class PlaybackState(Enum):
-    STOPPED = 'STOPPED',
-    PLAYING = 'PLAYING',
+    STOPPED = 'STOPPED'
+    PLAYING = 'PLAYING'
     PAUSED = 'PAUSED'
 
 
 class RecordingState(Enum):
-    STOPPED = 'STOPPED',
-    RECORDING = 'RECORDING',
+    STOPPED = 'STOPPED'
+    RECORDING = 'RECORDING'
     PAUSED = 'PAUSED'
 
 
@@ -55,10 +54,14 @@ class SoundPlugin(Plugin):
     _STREAM_NAME_PREFIX = 'platypush-stream-'
     _default_input_stream_fifo = os.path.join(tempfile.gettempdir(), 'inputstream')
 
-    # noinspection PyProtectedMember
-    def __init__(self, input_device=None, output_device=None,
+    def __init__(
+        self,
+        input_device=None,
+        output_device=None,
         input_blocksize=Sound._DEFAULT_BLOCKSIZE,
-                 output_blocksize=Sound._DEFAULT_BLOCKSIZE, **kwargs):
+        output_blocksize=Sound._DEFAULT_BLOCKSIZE,
+        **kwargs,
+    ):
         """
         :param input_device: Index or name of the default input device. Use
             :meth:`platypush.plugins.sound.query_devices` to get the
@@ -110,6 +113,7 @@ class SoundPlugin(Plugin):
         """
 
         import sounddevice as sd
+
         return sd.query_hostapis()[0].get('default_' + category.lower() + '_device')
 
     @action
@@ -174,17 +178,18 @@ class SoundPlugin(Plugin):
                 self.playback_paused_changed[stream_index].wait()
 
             if frames != blocksize:
-                self.logger.warning('Received {} frames, expected blocksize is {}'.
-                                    format(frames, blocksize))
+                self.logger.warning(
+                    'Received %d frames, expected blocksize is %d', frames, blocksize
+                )
                 return
 
             if status.output_underflow:
                 self.logger.warning('Output underflow: increase blocksize?')
-                outdata[:] = (b'\x00' if is_raw_stream else 0.) * len(outdata)
+                outdata[:] = (b'\x00' if is_raw_stream else 0.0) * len(outdata)
                 return
 
             if status:
-                self.logger.warning('Audio callback failed: {}'.format(status))
+                self.logger.warning('Audio callback failed: %s', status)
 
             try:
                 data = q.get_nowait()
@@ -193,18 +198,28 @@ class SoundPlugin(Plugin):
                 raise sd.CallbackStop
 
             if len(data) < len(outdata):
-                outdata[:len(data)] = data
-                outdata[len(data):] = (b'\x00' if is_raw_stream else 0.) * \
-                                      (len(outdata) - len(data))
+                outdata[: len(data)] = data
+                outdata[len(data) :] = (b'\x00' if is_raw_stream else 0.0) * (
+                    len(outdata) - len(data)
+                )
             else:
                 outdata[:] = data
 
         return audio_callback
 
     @action
-    def play(self, file=None, sound=None, device=None, blocksize=None,
-             bufsize=None, samplerate=None, channels=None, stream_name=None,
-             stream_index=None):
+    def play(
+        self,
+        file=None,
+        sound=None,
+        device=None,
+        blocksize=None,
+        bufsize=None,
+        samplerate=None,
+        channels=None,
+        stream_name=None,
+        stream_index=None,
+    ):
         """
         Plays a sound file (support formats: wav, raw) or a synthetic sound.
 
@@ -258,8 +273,9 @@ class SoundPlugin(Plugin):
         """
 
         if not file and not sound:
-            raise RuntimeError('Please specify either a file to play or a ' +
-                               'list of sound objects')
+            raise RuntimeError(
+                'Please specify either a file to play or a ' + 'list of sound objects'
+            )
 
         import sounddevice as sd
 
@@ -274,7 +290,7 @@ class SoundPlugin(Plugin):
 
         q = queue.Queue(maxsize=bufsize)
         f = None
-        t = 0.
+        t = 0.0
 
         if file:
             file = os.path.abspath(os.path.expanduser(file))
@@ -286,6 +302,7 @@ class SoundPlugin(Plugin):
 
         if file:
             import soundfile as sf
+
             f = sf.SoundFile(file)
         if not samplerate:
             samplerate = f.samplerate if f else Sound._DEFAULT_SAMPLERATE
@@ -295,7 +312,8 @@ class SoundPlugin(Plugin):
         mix = None
         with self.playback_state_lock:
             stream_index, is_new_stream = self._get_or_allocate_stream_index(
-                stream_index=stream_index, stream_name=stream_name)
+                stream_index=stream_index, stream_name=stream_name
+            )
 
             if sound and stream_index in self.stream_mixes:
                 mix = self.stream_mixes[stream_index]
@@ -304,9 +322,12 @@ class SoundPlugin(Plugin):
         if not mix:
             return None, "Unable to allocate the stream"
 
-        self.logger.info(('Starting playback of {} to sound device [{}] ' +
-                          'on stream [{}]').format(
-            file or sound, device, stream_index))
+        self.logger.info(
+            'Starting playback of %s to sound device [%s] on stream [%s]',
+            file or sound,
+            device,
+            stream_index,
+        )
 
         if not is_new_stream:
             return  # Let the existing callback handle the new mix
@@ -323,8 +344,11 @@ class SoundPlugin(Plugin):
                 else:
                     duration = mix.duration()
                     blocktime = float(blocksize / samplerate)
-                    next_t = min(t + blocktime, duration) \
-                        if duration is not None else t + blocktime
+                    next_t = (
+                        min(t + blocktime, duration)
+                        if duration is not None
+                        else t + blocktime
+                    )
 
                     data = mix.get_wave(t_start=t, t_end=next_t, samplerate=samplerate)
                     t = next_t
@@ -339,14 +363,20 @@ class SoundPlugin(Plugin):
 
             if stream is None:
                 streamtype = sd.RawOutputStream if file else sd.OutputStream
-                stream = streamtype(samplerate=samplerate, blocksize=blocksize,
-                                    device=device, channels=channels,
+                stream = streamtype(
+                    samplerate=samplerate,
+                    blocksize=blocksize,
+                    device=device,
+                    channels=channels,
                     dtype='float32',
                     callback=self._play_audio_callback(
-                                        q=q, blocksize=blocksize,
+                        q=q,
+                        blocksize=blocksize,
                         streamtype=streamtype,
-                                        stream_index=stream_index),
-                                    finished_callback=completed_callback_event.set)
+                        stream_index=stream_index,
+                    ),
+                    finished_callback=completed_callback_event.set,
+                )
 
                 self._start_playback(stream_index=stream_index, stream=stream)
 
@@ -356,8 +386,9 @@ class SoundPlugin(Plugin):
                 timeout = blocksize * bufsize / samplerate
 
                 while True:
-                    while self._get_playback_state(stream_index) == \
-                            PlaybackState.PAUSED:
+                    while (
+                        self._get_playback_state(stream_index) == PlaybackState.PAUSED
+                    ):
                         self.playback_paused_changed[stream_index].wait()
 
                     if f:
@@ -367,31 +398,38 @@ class SoundPlugin(Plugin):
                     else:
                         duration = mix.duration()
                         blocktime = float(blocksize / samplerate)
-                        next_t = min(t + blocktime, duration) \
-                            if duration is not None else t + blocktime
+                        next_t = (
+                            min(t + blocktime, duration)
+                            if duration is not None
+                            else t + blocktime
+                        )
 
-                        data = mix.get_wave(t_start=t, t_end=next_t,
-                                            samplerate=samplerate)
+                        data = mix.get_wave(
+                            t_start=t, t_end=next_t, samplerate=samplerate
+                        )
                         t = next_t
 
                         if duration is not None and t >= duration:
                             break
 
-                    if self._get_playback_state(stream_index) == \
-                            PlaybackState.STOPPED:
+                    if self._get_playback_state(stream_index) == PlaybackState.STOPPED:
                         break
 
                     try:
                         q.put(data, timeout=timeout)
                     except queue.Full as e:
-                        if self._get_playback_state(stream_index) != \
-                                PlaybackState.PAUSED:
+                        if (
+                            self._get_playback_state(stream_index)
+                            != PlaybackState.PAUSED
+                        ):
                             raise e
 
                 completed_callback_event.wait()
         except queue.Full:
-            if stream_index is None or \
-                    self._get_playback_state(stream_index) != PlaybackState.STOPPED:
+            if (
+                stream_index is None
+                or self._get_playback_state(stream_index) != PlaybackState.STOPPED
+            ):
                 self.logger.warning('Playback timeout: audio callback failed?')
         finally:
             if f and not f.closed:
@@ -400,35 +438,34 @@ class SoundPlugin(Plugin):
             self.stop_playback([stream_index])
 
     @action
-    def stream_recording(self, device=None, fifo=None, duration=None, sample_rate=None,
-                         dtype='float32', blocksize=None, latency=0, channels=1):
+    def stream_recording(
+        self,
+        device: Optional[str] = None,
+        fifo: Optional[str] = None,
+        duration: Optional[float] = None,
+        sample_rate: Optional[int] = None,
+        dtype: Optional[str] = 'float32',
+        blocksize: Optional[int] = None,
+        latency: float = 0,
+        channels: int = 1,
+    ):
         """
         Return audio data from an audio source
 
-        :param device: Input device (default: default configured device or system default audio input if not configured)
-        :type device: int or str
-
-        :param fifo: Path of the FIFO that will be used to exchange audio samples (default: /tmp/inputstream)
-        :type fifo: str
-
-        :param duration: Recording duration in seconds (default: record until stop event)
-        :type duration: float
-
+        :param device: Input device (default: default configured device or
+            system default audio input if not configured)
+        :param fifo: Path of the FIFO that will be used to exchange audio
+            samples (default: /tmp/inputstream)
+        :param duration: Recording duration in seconds (default: record until
+            stop event)
         :param sample_rate: Recording sample rate (default: device default rate)
-        :type sample_rate: int
-
         :param dtype: Data type for the audio samples. Supported types:
-            'float64', 'float32', 'int32', 'int16', 'int8', 'uint8'. Default: float32
-        :type dtype: str
-
-        :param blocksize: Audio block size (default: configured `input_blocksize` or 2048)
-        :type blocksize: int
-
+            'float64', 'float32', 'int32', 'int16', 'int8', 'uint8'. Default:
+            float32
+        :param blocksize: Audio block size (default: configured
+            `input_blocksize` or 2048)
         :param latency: Device latency in seconds (default: 0)
-        :type latency: float
-
         :param channels: Number of channels (default: 1)
-        :type channels: int
         """
 
         import sounddevice as sd
@@ -452,37 +489,49 @@ class SoundPlugin(Plugin):
 
         q = queue.Queue()
 
-        # noinspection PyUnusedLocal
-        def audio_callback(indata, frames, time_duration, status):
+        def audio_callback(indata, frames, time_duration, status):  # noqa
             while self._get_recording_state() == RecordingState.PAUSED:
                 self.recording_paused_changed.wait()
 
             if status:
-                self.logger.warning('Recording callback status: {}'.format(str(status)))
+                self.logger.warning('Recording callback status: %s', status)
 
             q.put(indata.copy())
 
         def streaming_thread():
             try:
-                with sd.InputStream(samplerate=sample_rate, device=device,
-                                    channels=channels, callback=audio_callback,
-                                    dtype=dtype, latency=latency, blocksize=blocksize):
-                    with open(fifo, 'wb') as audio_queue:
+                with sd.InputStream(
+                    samplerate=sample_rate,
+                    device=device,
+                    channels=channels,
+                    callback=audio_callback,
+                    dtype=dtype,
+                    latency=latency,
+                    blocksize=blocksize,
+                ), open(fifo, 'wb') as audio_queue:
                     self.start_recording()
                     get_bus().post(SoundRecordingStartedEvent())
-                        self.logger.info('Started recording from device [{}]'.format(device))
+                    self.logger.info('Started recording from device [%s]', device)
                     recording_started_time = time.time()
 
-                        while self._get_recording_state() != RecordingState.STOPPED \
-                                and (duration is None or
-                                     time.time() - recording_started_time < duration):
+                    while self._get_recording_state() != RecordingState.STOPPED and (
+                        duration is None
+                        or time.time() - recording_started_time < duration
+                    ):
                         while self._get_recording_state() == RecordingState.PAUSED:
                             self.recording_paused_changed.wait()
 
-                            get_args = {
+                        get_args = (
+                            {
                                 'block': True,
-                                'timeout': max(0, duration - (time.time() - recording_started_time)),
-                            } if duration is not None else {}
+                                'timeout': max(
+                                    0,
+                                    duration - (time.time() - recording_started_time),
+                                ),
+                            }
+                            if duration is not None
+                            else {}
+                        )
 
                         data = q.get(**get_args)
                         if not len(data):
@@ -497,17 +546,29 @@ class SoundPlugin(Plugin):
 
         if os.path.exists(fifo):
             if stat.S_ISFIFO(os.stat(fifo).st_mode):
-                self.logger.info('Removing previous input stream FIFO {}'.format(fifo))
+                self.logger.info('Removing previous input stream FIFO %s', fifo)
                 os.unlink(fifo)
             else:
-                raise RuntimeError('{} exists and is not a FIFO. Please remove it or rename it'.format(fifo))
+                raise RuntimeError(
+                    f'{fifo} exists and is not a FIFO. Please remove it or rename it'
+                )
 
         os.mkfifo(fifo, 0o644)
         Thread(target=streaming_thread).start()
 
     @action
-    def record(self, outfile=None, duration=None, device=None, sample_rate=None,
-               format=None, blocksize=None, latency=0, channels=1, subtype='PCM_24'):
+    def record(
+        self,
+        outfile=None,
+        duration=None,
+        device=None,
+        sample_rate=None,
+        format=None,
+        blocksize=None,
+        latency=0,
+        channels=1,
+        subtype='PCM_24',
+    ):
         """
         Records audio to a sound file (support formats: wav, raw)
 
@@ -535,12 +596,23 @@ class SoundPlugin(Plugin):
         :param channels: Number of channels (default: 1)
         :type channels: int
 
-        :param subtype: Recording subtype - see `Soundfile docs - Subtypes <https://pysoundfile.readthedocs.io/en/0.9.0/#soundfile.available_subtypes>`_ for a list of the available subtypes (default: PCM_24)
+        :param subtype: Recording subtype - see `Soundfile docs - Subtypes
+            <https://pysoundfile.readthedocs.io/en/0.9.0/#soundfile.available_subtypes>`_
+            for a list of the available subtypes (default: PCM_24)
         :type subtype: str
         """
 
-        def recording_thread(outfile, duration, device, sample_rate, format,
-                             blocksize, latency, channels, subtype):
+        def recording_thread(
+            outfile,
+            duration,
+            device,
+            sample_rate,
+            format,
+            blocksize,
+            latency,
+            channels,
+            subtype,
+        ):
             import sounddevice as sd
 
             self.recording_paused_changed.clear()
@@ -548,12 +620,15 @@ class SoundPlugin(Plugin):
             if outfile:
                 outfile = os.path.abspath(os.path.expanduser(outfile))
                 if os.path.isfile(outfile):
-                    self.logger.info('Removing existing audio file {}'.format(outfile))
+                    self.logger.info('Removing existing audio file %s', outfile)
                     os.unlink(outfile)
             else:
                 outfile = tempfile.NamedTemporaryFile(
-                    prefix='recording_', suffix='.wav', delete=False,
-                    dir=tempfile.gettempdir()).name
+                    prefix='recording_',
+                    suffix='.wav',
+                    delete=False,
+                    dir=tempfile.gettempdir(),
+                ).name
 
             if device is None:
                 device = self.input_device
@@ -574,42 +649,68 @@ class SoundPlugin(Plugin):
                     self.recording_paused_changed.wait()
 
                 if status:
-                    self.logger.warning('Recording callback status: {}'.format(
-                        str(status)))
+                    self.logger.warning('Recording callback status: %s', status)
 
-                q.put({
+                q.put(
+                    {
                         'timestamp': time.time(),
                         'frames': frames,
                         'time': duration,
-                    'data': indata.copy()
-                })
+                        'data': indata.copy(),
+                    }
+                )
 
             try:
                 import soundfile as sf
-                import numpy
 
-                with sf.SoundFile(outfile, mode='w', samplerate=sample_rate,
-                                  format=format, channels=channels, subtype=subtype) as f:
-                    with sd.InputStream(samplerate=sample_rate, device=device,
-                                        channels=channels, callback=audio_callback,
-                                        latency=latency, blocksize=blocksize):
+                with sf.SoundFile(
+                    outfile,
+                    mode='w',
+                    samplerate=sample_rate,
+                    format=format,
+                    channels=channels,
+                    subtype=subtype,
+                ) as f:
+                    with sd.InputStream(
+                        samplerate=sample_rate,
+                        device=device,
+                        channels=channels,
+                        callback=audio_callback,
+                        latency=latency,
+                        blocksize=blocksize,
+                    ):
                         self.start_recording()
                         get_bus().post(SoundRecordingStartedEvent(filename=outfile))
-                        self.logger.info('Started recording from device [{}] to [{}]'.
-                                         format(device, outfile))
+                        self.logger.info(
+                            'Started recording from device [%s] to [%s]',
+                            device,
+                            outfile,
+                        )
 
                         recording_started_time = time.time()
 
-                        while self._get_recording_state() != RecordingState.STOPPED \
-                                and (duration is None or
-                                     time.time() - recording_started_time < duration):
+                        while (
+                            self._get_recording_state() != RecordingState.STOPPED
+                            and (
+                                duration is None
+                                or time.time() - recording_started_time < duration
+                            )
+                        ):
                             while self._get_recording_state() == RecordingState.PAUSED:
                                 self.recording_paused_changed.wait()
 
-                            get_args = {
+                            get_args = (
+                                {
                                     'block': True,
-                                'timeout': max(0, duration - (time.time() - recording_started_time)),
-                            } if duration is not None else {}
+                                    'timeout': max(
+                                        0,
+                                        duration
+                                        - (time.time() - recording_started_time),
+                                    ),
+                                }
+                                if duration is not None
+                                else {}
+                            )
 
                             data = q.get(**get_args)
                             if data and time.time() - data.get('timestamp') <= 1.0:
@@ -624,24 +725,45 @@ class SoundPlugin(Plugin):
                 self.stop_recording()
                 get_bus().post(SoundRecordingStoppedEvent(filename=outfile))
 
-        Thread(target=recording_thread,
+        Thread(
+            target=recording_thread,
             args=(
-                   outfile, duration, device, sample_rate, format, blocksize, latency, channels, subtype)
+                outfile,
+                duration,
+                device,
+                sample_rate,
+                format,
+                blocksize,
+                latency,
+                channels,
+                subtype,
+            ),
         ).start()
 
     @action
-    def recordplay(self, duration=None, input_device=None, output_device=None,
-                   sample_rate=None, blocksize=None, latency=0, channels=1, dtype=None):
+    def recordplay(
+        self,
+        duration=None,
+        input_device=None,
+        output_device=None,
+        sample_rate=None,
+        blocksize=None,
+        latency=0,
+        channels=1,
+        dtype=None,
+    ):
         """
         Records audio and plays it on an output sound device (audio pass-through)
 
         :param duration: Recording duration in seconds (default: record until stop event)
         :type duration: float
 
-        :param input_device: Input device (default: default configured device or system default audio input if not configured)
+        :param input_device: Input device (default: default configured device
+            or system default audio input if not configured)
         :type input_device: int or str
 
-        :param output_device: Output device (default: default configured device or system default audio output if not configured)
+        :param output_device: Output device (default: default configured device
+            or system default audio output if not configured)
         :type output_device: int or str
 
         :param sample_rate: Recording sample rate (default: device default rate)
@@ -656,7 +778,10 @@ class SoundPlugin(Plugin):
         :param channels: Number of channels (default: 1)
         :type channels: int
 
-        :param dtype: Data type for the recording - see `Soundfile docs - Recording <https://python-sounddevice.readthedocs.io/en/0.3.12/_modules/sounddevice.html#rec>`_ for available types (default: input device default)
+        :param dtype: Data type for the recording - see `Soundfile docs -
+            Recording
+            <https://python-sounddevice.readthedocs.io/en/0.3.12/_modules/sounddevice.html#rec>`_
+            for available types (default: input device default)
         :type dtype: str
         """
 
@@ -687,35 +812,37 @@ class SoundPlugin(Plugin):
                 self.recording_paused_changed.wait()
 
             if status:
-                self.logger.warning('Recording callback status: {}'.format(
-                    str(status)))
+                self.logger.warning('Recording callback status: %s', status)
 
             outdata[:] = indata
 
         stream_index = None
 
         try:
-            import soundfile as sf
-            import numpy
-
             stream_index = self._allocate_stream_index()
-            stream = sd.Stream(samplerate=sample_rate, channels=channels,
-                               blocksize=blocksize, latency=latency,
+            stream = sd.Stream(
+                samplerate=sample_rate,
+                channels=channels,
+                blocksize=blocksize,
+                latency=latency,
                 device=(input_device, output_device),
-                               dtype=dtype, callback=audio_callback)
+                dtype=dtype,
+                callback=audio_callback,
+            )
             self.start_recording()
-            self._start_playback(stream_index=stream_index,
-                                 stream=stream)
+            self._start_playback(stream_index=stream_index, stream=stream)
 
-            self.logger.info('Started recording pass-through from device ' +
-                             '[{}] to sound device [{}]'.
-                             format(input_device, output_device))
+            self.logger.info(
+                'Started recording pass-through from device [%s] to sound device [%s]',
+                input_device,
+                output_device,
+            )
 
             recording_started_time = time.time()
 
-            while self._get_recording_state() != RecordingState.STOPPED \
-                    and (duration is None or
-                         time.time() - recording_started_time < duration):
+            while self._get_recording_state() != RecordingState.STOPPED and (
+                duration is None or time.time() - recording_started_time < duration
+            ):
                 while self._get_recording_state() == RecordingState.PAUSED:
                     self.recording_paused_changed.wait()
 
@@ -736,24 +863,35 @@ class SoundPlugin(Plugin):
         streams = {
             i: {
                 attr: getattr(stream, attr)
-                for attr in ['active', 'closed', 'stopped', 'blocksize',
-                             'channels', 'cpu_load', 'device', 'dtype',
-                             'latency', 'samplerate', 'samplesize']
+                for attr in [
+                    'active',
+                    'closed',
+                    'stopped',
+                    'blocksize',
+                    'channels',
+                    'cpu_load',
+                    'device',
+                    'dtype',
+                    'latency',
+                    'samplerate',
+                    'samplesize',
+                ]
                 if hasattr(stream, attr)
-            } for i, stream in self.active_streams.items()
+            }
+            for i, stream in self.active_streams.items()
         }
 
         for i, stream in streams.items():
             stream['playback_state'] = self.playback_state[i].name
             stream['name'] = self.stream_index_to_name.get(i)
             if i in self.stream_mixes:
-                stream['mix'] = {j: sound for j, sound in
-                                 enumerate(list(self.stream_mixes[i]))}
+                stream['mix'] = dict(enumerate(list(self.stream_mixes[i])))
 
         return streams
 
-    def _get_or_allocate_stream_index(self, stream_index=None, stream_name=None,
-                                      completed_callback_event=None):
+    def _get_or_allocate_stream_index(
+        self, stream_index=None, stream_name=None, completed_callback_event=None
+    ):
         stream = None
 
         with self.playback_state_lock:
@@ -762,22 +900,26 @@ class SoundPlugin(Plugin):
                     stream_index = self.stream_name_to_index.get(stream_name)
             else:
                 if stream_name is not None:
-                    raise RuntimeError('Redundant specification of both ' +
-                                       'stream_name and stream_index')
+                    raise RuntimeError(
+                        'Redundant specification of both '
+                        + 'stream_name and stream_index'
+                    )
 
             if stream_index is not None:
                 stream = self.active_streams.get(stream_index)
 
             if not stream:
-                return (self._allocate_stream_index(stream_name=stream_name,
-                                                    completed_callback_event=
-                                                    completed_callback_event),
-                        True)
+                return (
+                    self._allocate_stream_index(
+                        stream_name=stream_name,
+                        completed_callback_event=completed_callback_event,
+                    ),
+                    True,
+                )
 
             return stream_index, False
 
-    def _allocate_stream_index(self, stream_name=None,
-                               completed_callback_event=None):
+    def _allocate_stream_index(self, stream_name=None, completed_callback_event=None):
         stream_index = None
 
         with self.playback_state_lock:
@@ -796,8 +938,9 @@ class SoundPlugin(Plugin):
             self.stream_mixes[stream_index] = Mix()
             self.stream_index_to_name[stream_index] = stream_name
             self.stream_name_to_index[stream_name] = stream_index
-            self.completed_callback_events[stream_index] = \
+            self.completed_callback_events[stream_index] = (
                 completed_callback_event if completed_callback_event else Event()
+            )
 
         return stream_index
 
@@ -811,8 +954,7 @@ class SoundPlugin(Plugin):
             else:
                 self.playback_paused_changed[stream_index] = Event()
 
-        self.logger.info('Playback started on stream index {}'.
-                         format(stream_index))
+        self.logger.info('Playback started on stream index %d', stream_index)
 
         return stream_index
 
@@ -835,8 +977,7 @@ class SoundPlugin(Plugin):
                     i = self.stream_name_to_index.get(i)
                     stream = self.active_streams.get(i)
                 if not stream:
-                    self.logger.info('No such stream index or name: {}'.
-                                     format(i))
+                    self.logger.info('No such stream index or name: %d', i)
                     continue
 
                 if self.completed_callback_events[i]:
@@ -859,9 +1000,10 @@ class SoundPlugin(Plugin):
                 if name in self.stream_name_to_index:
                     del self.stream_name_to_index[name]
 
-        self.logger.info('Playback stopped on streams [{}]'.format(
-            ', '.join([str(stream) for stream in
-                       completed_callback_events.keys()])))
+        self.logger.info(
+            'Playback stopped on streams [%s]',
+            ', '.join([str(stream) for stream in completed_callback_events]),
+        )
 
     @action
     def pause_playback(self, streams=None):
@@ -881,8 +1023,7 @@ class SoundPlugin(Plugin):
                     i = self.stream_name_to_index.get(i)
                     stream = self.active_streams.get(i)
                 if not stream:
-                    self.logger.info('No such stream index or name: {}'.
-                                     format(i))
+                    self.logger.info('No such stream index or name: %d', i)
                     continue
 
                 if self.playback_state[i] == PlaybackState.PAUSED:
@@ -894,8 +1035,10 @@ class SoundPlugin(Plugin):
 
                 self.playback_paused_changed[i].set()
 
-        self.logger.info('Playback pause toggled on streams [{}]'.format(
-            ', '.join([str(stream) for stream in streams])))
+        self.logger.info(
+            'Playback pause toggled on streams [%s]',
+            ', '.join([str(stream) for stream in streams]),
+        )
 
     def start_recording(self):
         with self.recording_state_lock:
@@ -921,8 +1064,14 @@ class SoundPlugin(Plugin):
         self.recording_paused_changed.set()
 
     @action
-    def release(self, stream_index=None, stream_name=None,
-                sound_index=None, midi_note=None, frequency=None):
+    def release(
+        self,
+        stream_index=None,
+        stream_name=None,
+        sound_index=None,
+        midi_note=None,
+        frequency=None,
+    ):
         """
         Remove a sound from an active stream, either by sound index (use
             :meth:`platypush.sound.plugin.SoundPlugin.query_streams` to get
@@ -949,25 +1098,26 @@ class SoundPlugin(Plugin):
 
         if stream_name:
             if stream_index:
-                raise RuntimeError('stream_index and stream name are ' +
-                                   'mutually exclusive')
+                raise RuntimeError(
+                    'stream_index and stream name are ' + 'mutually exclusive'
+                )
             stream_index = self.stream_name_to_index.get(stream_name)
 
-        mixes = {
-            i: mix for i, mix in self.stream_mixes.items()
-        } if stream_index is None else {
-            stream_index: self.stream_mixes[stream_index]
-        }
+        mixes = (
+            self.stream_mixes.copy()
+            if stream_index is None
+            else {stream_index: self.stream_mixes[stream_index]}
+        )
 
         streams_to_stop = []
 
         for i, mix in mixes.items():
             for j, sound in enumerate(mix):
-                if (sound_index is not None and j == sound_index) or \
-                        (midi_note is not None
-                         and sound.get('midi_note') == midi_note) or \
-                        (frequency is not None
-                         and sound.get('frequency') == frequency):
+                if (
+                    (sound_index is not None and j == sound_index)
+                    or (midi_note is not None and sound.get('midi_note') == midi_note)
+                    or (frequency is not None and sound.get('frequency') == frequency)
+                ):
                     if len(list(mix)) == 1:
                         # Last sound in the mix
                         streams_to_stop.append(i)

platypush/plugins/sound/core.py

@@ -1,7 +1,3 @@
-"""
-.. moduleauthor:: Fabio Manganiello <blacklight86@gmail.com>
-"""
-
 import enum
 import logging
 import json
@@ -15,7 +11,7 @@ class WaveShape(enum.Enum):
     TRIANG = 'triang'
 
 
-class Sound(object):
+class Sound:
     """
     Models a basic synthetic sound that can be played through an audio device
     """
@@ -34,9 +30,16 @@ class Sound(object):
     duration = None
     shape = None
 
-    def __init__(self, midi_note=midi_note, frequency=None, phase=phase,
-                 gain=gain, duration=duration, shape=WaveShape.SIN,
-                 A_frequency=STANDARD_A_FREQUENCY):
+    def __init__(
+        self,
+        midi_note=midi_note,
+        frequency=None,
+        phase=phase,
+        gain=gain,
+        duration=duration,
+        shape=WaveShape.SIN,
+        A_frequency=STANDARD_A_FREQUENCY,
+    ):
         """
         You can construct a sound either from a MIDI note or a base frequency
 
@@ -67,20 +70,24 @@ class Sound(object):
         """
 
         if midi_note and frequency:
-            raise RuntimeError('Please specify either a MIDI note or a base ' +
-                               'frequency')
+            raise RuntimeError(
+                'Please specify either a MIDI note or a base ' + 'frequency'
+            )
 
         if midi_note:
             self.midi_note = midi_note
-            self.frequency = self.note_to_freq(midi_note=midi_note,
-                                               A_frequency=A_frequency)
+            self.frequency = self.note_to_freq(
+                midi_note=midi_note, A_frequency=A_frequency
+            )
         elif frequency:
             self.frequency = frequency
-            self.midi_note = self.freq_to_note(frequency=frequency,
-                                               A_frequency=A_frequency)
+            self.midi_note = self.freq_to_note(
+                frequency=frequency, A_frequency=A_frequency
+            )
         else:
-            raise RuntimeError('Please specify either a MIDI note or a base ' +
-                               'frequency')
+            raise RuntimeError(
+                'Please specify either a MIDI note or a base ' + 'frequency'
+            )
 
         self.phase = phase
         self.gain = gain
@@ -99,8 +106,7 @@ class Sound(object):
         :type A_frequency: float
         """
 
-        return (2.0 ** ((midi_note - cls.STANDARD_A_MIDI_NOTE) / 12.0)) \
-               * A_frequency
+        return (2.0 ** ((midi_note - cls.STANDARD_A_MIDI_NOTE) / 12.0)) * A_frequency
 
     @classmethod
     def freq_to_note(cls, frequency, A_frequency=STANDARD_A_FREQUENCY):
@@ -116,10 +122,11 @@ class Sound(object):
 
         # TODO return also the offset in % between the provided frequency
         # and the standard MIDI note frequency
-        return int(12.0 * math.log(frequency / A_frequency, 2)
-                   + cls.STANDARD_A_MIDI_NOTE)
+        return int(
+            12.0 * math.log(frequency / A_frequency, 2) + cls.STANDARD_A_MIDI_NOTE
+        )
 
-    def get_wave(self, t_start=0., t_end=0., samplerate=_DEFAULT_SAMPLERATE):
+    def get_wave(self, t_start=0.0, t_end=0.0, samplerate=_DEFAULT_SAMPLERATE):
         """
         Get the wave binary data associated to this sound
 
@@ -137,6 +144,7 @@ class Sound(object):
         """
 
         import numpy as np
+
         x = np.linspace(t_start, t_end, int((t_end - t_start) * samplerate))
 
         x = x.reshape(len(x), 1)
@@ -148,8 +156,7 @@ class Sound(object):
                 wave[wave < 0] = -1
                 wave[wave >= 0] = 1
         elif self.shape == WaveShape.SAWTOOTH or self.shape == WaveShape.TRIANG:
-            wave = 2 * (self.frequency * x -
-                        np.floor(0.5 + self.frequency * x))
+            wave = 2 * (self.frequency * x - np.floor(0.5 + self.frequency * x))
             if self.shape == WaveShape.TRIANG:
                 wave = 2 * np.abs(wave) - 1
         else:
@@ -157,8 +164,14 @@ class Sound(object):
 
         return self.gain * wave
 
-    def fft(self, t_start=0., t_end=0., samplerate=_DEFAULT_SAMPLERATE,
-            freq_range=None, freq_buckets=None):
+    def fft(
+        self,
+        t_start=0.0,
+        t_end=0.0,
+        samplerate=_DEFAULT_SAMPLERATE,
+        freq_range=None,
+        freq_buckets=None,
+    ):
         """
         Get the real part of the Fourier transform associated to a time-bounded
             sample of this sound
@@ -173,7 +186,8 @@ class Sound(object):
         :type samplerate: int
 
         :param freq_range: FFT frequency range. Default: ``(0, samplerate/2)``
-            (see `Nyquist-Shannon sampling theorem <https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem>`_)
+            (see`Nyquist-Shannon sampling theorem
+            <https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem>`_)
         :type freq_range: list or tuple with 2 int elements (range)
 
         :param freq_buckets: Number of buckets to subdivide the frequency range.
@@ -190,7 +204,7 @@ class Sound(object):
 
         wave = self.get_wave(t_start=t_start, t_end=t_end, samplerate=samplerate)
         fft = np.fft.fft(wave.reshape(len(wave)))
-        fft = fft.real[freq_range[0]:freq_range[1]]
+        fft = fft.real[freq_range[0] : freq_range[1]]
 
         if freq_buckets is not None:
             fft = np.histogram(fft, bins=freq_buckets)
@@ -224,7 +238,7 @@ class Sound(object):
         raise RuntimeError('Usage: {}'.format(__doc__))
 
 
-class Mix(object):
+class Mix:
     """
     This class models a set of mixed :class:`Sound` instances that can be played
     through an audio stream to an audio device
@@ -251,15 +265,22 @@ class Mix(object):
 
     def remove(self, sound_index):
         if sound_index >= len(self._sounds):
-            self.logger.error('No such sound index: {} in mix {}'.format(
-                sound_index, list(self)))
+            self.logger.error(
+                'No such sound index: {} in mix {}'.format(sound_index, list(self))
+            )
             return
 
         self._sounds.pop(sound_index)
 
     # noinspection PyProtectedMember
-    def get_wave(self, t_start=0., t_end=0., normalize_range=(-1.0, 1.0),
-                 on_clip='scale', samplerate=Sound._DEFAULT_SAMPLERATE):
+    def get_wave(
+        self,
+        t_start=0.0,
+        t_end=0.0,
+        normalize_range=(-1.0, 1.0),
+        on_clip='scale',
+        samplerate=Sound._DEFAULT_SAMPLERATE,
+    ):
         """
         Get the wave binary data associated to this mix
 
@@ -289,8 +310,9 @@ class Mix(object):
         wave = None
 
         for sound in self._sounds:
-            sound_wave = sound.get_wave(t_start=t_start, t_end=t_end,
-                                        samplerate=samplerate)
+            sound_wave = sound.get_wave(
+                t_start=t_start, t_end=t_end, samplerate=samplerate
+            )
 
             if wave is None:
                 wave = sound_wave
@@ -298,8 +320,9 @@ class Mix(object):
                 wave += sound_wave
 
         if normalize_range and len(wave):
-            scale_factor = (normalize_range[1] - normalize_range[0]) / \
-                           (wave.max() - wave.min())
+            scale_factor = (normalize_range[1] - normalize_range[0]) / (
+                wave.max() - wave.min()
+            )
 
             if scale_factor < 1.0:  # Wave clipping
                 if on_clip == 'scale':
@@ -308,14 +331,21 @@ class Mix(object):
                     wave[wave < normalize_range[0]] = normalize_range[0]
                     wave[wave > normalize_range[1]] = normalize_range[1]
                 else:
-                    raise RuntimeError('Supported values for "on_clip": ' +
-                                       '"scale" or "clip"')
+                    raise RuntimeError(
+                        'Supported values for "on_clip": ' + '"scale" or "clip"'
+                    )
 
         return wave
 
     # noinspection PyProtectedMember
-    def fft(self, t_start=0., t_end=0., samplerate=Sound._DEFAULT_SAMPLERATE,
-            freq_range=None, freq_buckets=None):
+    def fft(
+        self,
+        t_start=0.0,
+        t_end=0.0,
+        samplerate=Sound._DEFAULT_SAMPLERATE,
+        freq_range=None,
+        freq_buckets=None,
+    ):
         """
         Get the real part of the Fourier transform associated to a time-bounded
             sample of this mix
@@ -330,7 +360,8 @@ class Mix(object):
         :type samplerate: int
 
         :param freq_range: FFT frequency range. Default: ``(0, samplerate/2)``
-            (see `Nyquist-Shannon sampling theorem <https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem>`_)
+            (see `Nyquist-Shannon sampling theorem
+            <https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem>`_)
         :type freq_range: list or tuple with 2 int elements (range)
 
         :param freq_buckets: Number of buckets to subdivide the frequency range.
@@ -347,7 +378,7 @@ class Mix(object):
 
         wave = self.get_wave(t_start=t_start, t_end=t_end, samplerate=samplerate)
         fft = np.fft.fft(wave.reshape(len(wave)))
-        fft = fft.real[freq_range[0]:freq_range[1]]
+        fft = fft.real[freq_range[0] : freq_range[1]]
 
         if freq_buckets is not None:
             fft = np.histogram(fft, bins=freq_buckets)
@@ -370,4 +401,5 @@ class Mix(object):
 
         return duration
 
+
 # vim:sw=4:ts=4:et: