用ButtonJupiterNotebook殺死一個回圈？

我想要：

• 從串口讀取（無限回圈）
• 當按下“停止”按鈕時 --> 停止讀取并繪制資料

從

uj5u.com熱心網友回復：

我認為問題就像在所有具有長時間運行代碼的 Python 腳本中一樣 - 它在一個執行緒中運行所有代碼，并且當它運行while True回圈（長時間運行代碼）時，它不能同時運行其他函式。

您可能必須在單獨的執行緒中運行您的函式 - 然后主執行緒可以執行on_button_clicked

這個版本適用于我：

from IPython.display import display
import ipywidgets as widgets
import time
import threading

button = widgets.Button(description="STOP!") 
output = widgets.Output()

display(button, output)

break_cicle = True

def on_button_clicked(event):
    global break_cicle
    
    break_cicle = False

    print("Button pressed: break_cicle:", break_cicle)
    
button.on_click(on_button_clicked)

def function():
    while break_cicle:
        print("While loop: break_cicle:", break_cicle)
        time.sleep(1)
    print("Done")
    
threading.Thread(target=function).start()

也許 Jupyter 有其他方法可以解決這個問題 - 即。當您使用asyncthen 撰寫函式時，您可以使用asyncio.sleep()which 讓 Python 在該函式處于休眠狀態時運行其他函式。

編輯：

在互聯網上挖掘（使用谷歌）我在 Jyputer 論壇上找到了帖子

執行長時間運行的單元格時的互動式小部件 - JupyterLab - Jupyter Community Forum

并且有指向模塊jupyter-ui-poll的鏈接，該模塊顯示了類似的示例（while-loop Button）并events用于此目的。當函式pull()執行時（在每個回圈中），Jupyter 可以將事件發送到小部件并且它有時間執行on_click()。

import time
from ipywidgets import Button
from jupyter_ui_poll import ui_events

# Set up simple GUI, button with on_click callback
# that sets ui_done=True and changes button text
ui_done = False
def on_click(btn):
    global ui_done
    ui_done = True
    btn.description = '??'

btn = Button(description='Click Me')
btn.on_click(on_click)
display(btn)

# Wait for user to press the button
with ui_events() as poll:
    while ui_done is False:
        poll(10)          # React to UI events (upto 10 at a time)
        print('.', end='')
        time.sleep(0.1)
print('done')

在源代碼中，我可以看到它asyncio用于此目的。

編輯：

多處理版本

行程不共享變數，因此它需要Queue將資訊從一個行程發送到另一個行程。

示例將訊息從 發送button到function。如果您想從中發送訊息function，button那么最好使用第二個佇列。

from IPython.display import display
import ipywidgets as widgets
import time
import multiprocessing

button = widgets.Button(description="STOP!") 
output = widgets.Output()

display(button, output)

queue = multiprocessing.Queue()

def on_button_clicked(event):
    queue.put('stop')
    print("Button pressed")
    
button.on_click(on_button_clicked)

def function(queue):
    
    while True:
        print("While loop")
        time.sleep(1)
        
        if not queue.empty():
            msg = queue.get()
            if msg == 'stop':
                break
            #if msg == 'other text':             
            #    ...other code...
            
    print("Done")
    
multiprocessing.Process(target=function, args=(queue,)).start()

或更類似于以前的

def function(queue):

    break_cicle = True
    
    while break_cicle:
        print("While loop: break_cicle:", break_cicle)
        time.sleep(1)
        
        if (not queue.empty()) and (queue.get() == 'stop'):
            break_cicle = False
        
    print("Done")

編輯：

帶異步的版本

Jupyter already is running asynio event loop and I add async function to this loop. And function uses await functions like asyncio.sleep so asynio event loop has time to run other functions - but if function could run only standard (not async) functions then it wouldn't work.

from IPython.display import display
import ipywidgets as widgets
import asyncio

button = widgets.Button(description="STOP!") 
output = widgets.Output()

display(button, output)

break_cicle = True

def on_button_clicked(event):
    global break_cicle
    
    break_cicle = False

    print("Button pressed: break_cicle:", break_cicle)
    
button.on_click(on_button_clicked)

async def function():   # it has to be `async`
    while break_cicle:
        print("While loop: break_cicle:", break_cicle)
        await asyncio.sleep(1)   # it needs some `await` functions
    print("Done")
    
loop = asyncio.get_event_loop()    
t = loop.create_task(function())  # assign to variable if you don't want to see `<Task ...>` in output

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