going to try to merge asyncio loop into kivy loop
quadrismegistus
4 years ago
parent
c7fc80e65a
commit
c850d9894f
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"""
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Kivy asyncio example app.
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Kivy needs to run on the main thread and its graphical instructions have to be
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called from there. But it's still possible to run an asyncio EventLoop, it
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just has to happen on its own, separate thread.
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Requires Python 3.5+.
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"""
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import kivy
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kivy.require('1.10.0')
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import asyncio
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import threading
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from kivy.app import App
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from kivy.clock import mainthread
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from kivy.event import EventDispatcher
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from kivy.lang import Builder
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from kivy.uix.boxlayout import BoxLayout
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KV = '''\
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<RootLayout>:
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orientation: 'vertical'
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Button:
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id: btn
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text: 'Start EventLoop thread.'
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on_press: app.start_event_loop_thread()
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TextInput:
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multiline: False
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size_hint_y: 0.25
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on_text: app.submit_pulse_text(args[1])
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BoxLayout:
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Label:
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id: pulse_listener
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Label:
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id: status
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'''
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class RootLayout(BoxLayout):
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pass
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class EventLoopWorker(EventDispatcher):
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__events__ = ('on_pulse',) # defines this EventDispatcher's sole event
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def __init__(self):
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super().__init__()
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self._thread = threading.Thread(target=self._run_loop) # note the Thread target here
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self._thread.daemon = True
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self.loop = None
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# the following are for the pulse() coroutine, see below
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self._default_pulse = ['tick!', 'tock!']
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self._pulse = None
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self._pulse_task = None
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def _run_loop(self):
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self.loop = asyncio.get_event_loop_policy().new_event_loop()
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asyncio.set_event_loop(self.loop)
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self._restart_pulse()
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# this example doesn't include any cleanup code, see the docs on how
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# to properly set up and tear down an asyncio event loop
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self.loop.run_forever()
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def start(self):
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self._thread.start()
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async def pulse(self):
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"""Core coroutine of this asyncio event loop.
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Repeats a pulse message in a short interval on three channels:
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- using `print()`
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- by dispatching a Kivy event `on_pulse` with the help of `@mainthread`
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- on the Kivy thread through `kivy_update_status()` with the help of
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`@mainthread`
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The decorator `@mainthread` is a convenience wrapper around
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`Clock.schedule_once()` which ensures the callables run on the Kivy
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thread.
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"""
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for msg in self._pulse_messages():
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# show it through the console:
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print(msg)
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# `EventLoopWorker` is an `EventDispatcher` to which others can
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# subscribe. See `display_on_pulse()` in `start_event_loop_thread()`
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# on how it is bound to the `on_pulse` event. The indirection
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# through the `notify()` function is necessary to apply the
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# `@mainthread` decorator (left label):
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@mainthread
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def notify(text):
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self.dispatch('on_pulse', text)
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notify(msg) # dispatch the on_pulse event
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# Same, but with a direct call instead of an event (right label):
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@mainthread
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def kivy_update_status(text):
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status_label = App.get_running_app().root.ids.status
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status_label.text = text
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kivy_update_status(msg) # control a Label directly
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await asyncio.sleep(1)
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def set_pulse_text(self, text):
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self._pulse = text
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# it's not really necessary to restart this task; just included for the
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# sake of this example. Comment this line out and see what happens.
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self._restart_pulse()
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def _restart_pulse(self):
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"""Helper to start/reset the pulse task when the pulse changes."""
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if self._pulse_task is not None:
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self._pulse_task.cancel()
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self._pulse_task = self.loop.create_task(self.pulse())
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def on_pulse(self, *_):
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"""An EventDispatcher event must have a corresponding method."""
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pass
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def _pulse_messages(self):
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"""A generator providing an inexhaustible supply of pulse messages."""
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while True:
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if isinstance(self._pulse, str) and self._pulse != '':
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pulse = self._pulse.split()
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yield from pulse
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else:
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yield from self._default_pulse
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class AsyncioExampleApp(App):
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def __init__(self, **kwargs):
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super().__init__(**kwargs)
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self.event_loop_worker = None
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def build(self):
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return RootLayout()
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def start_event_loop_thread(self):
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"""Start the asyncio event loop thread. Bound to the top button."""
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if self.event_loop_worker is not None:
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return
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self.root.ids.btn.text = ("Running the asyncio EventLoop now...\n\n\n\n"
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"Now enter a few words below.")
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self.event_loop_worker = worker = EventLoopWorker()
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pulse_listener_label = self.root.ids.pulse_listener
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def display_on_pulse(instance, text):
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pulse_listener_label.text = text
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# make the label react to the worker's `on_pulse` event:
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worker.bind(on_pulse=display_on_pulse)
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worker.start()
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def submit_pulse_text(self, text):
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"""Send the TextInput string over to the asyncio event loop worker."""
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worker = self.event_loop_worker
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if worker is not None:
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loop = self.event_loop_worker.loop
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# use the thread safe variant to run it on the asyncio event loop:
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loop.call_soon_threadsafe(worker.set_pulse_text, text)
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if __name__ == '__main__':
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Builder.load_string(KV)
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AsyncioExampleApp().run()
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