python - Ipywidgets 生态系统中用于中断循环的停止按钮

Question

让我们假设以下问题:我们有一个 Ipywidget 按钮和一个进度条。单击按钮时，将执行函数 work()，它只会填充进度条直到完成，然后反转过程并将其清空。就目前而言，这样的功能会持续运行。以下代码片段提供了相应的 MWE:

# importing packages.
from IPython.display import display
import ipywidgets as widgets
import time
import functools

# setting 'progress', 'start_button' and 'Hbox' variables.
progress = widgets.FloatProgress(value=0.0, min=0.0, max=1.0)
start_button = widgets.Button(description="start fill")
Hbox = widgets.HBox(children=[start_button, progress])

# defining 'on_button_clicked_start()' function; executes 'work()' function.
def on_button_clicked_start(b, start_button, progress):
    work(progress)

# call to 'on_button_clicked_start()' function when clicking the button.
start_button.on_click(functools.partial(on_button_clicked_start, start_button=start_button, progress=progress))

# defining 'work()' function.
def work(progress):
    total = 100
    i = 0
    # while roop for continuous run.
    while True:
        # while loop for filling the progress bar.
        while progress.value < 1.0:
            time.sleep(0.01)
            i += 1
            progress.value = float(i)/total
        # while loop for emptying the progress bar.
        while progress.value > 0.0:
            time.sleep(0.01)
            i -= 1
            progress.value = float(i)/total
        
# display statement.
display(Hbox)

目标是包含“停止”和“恢复”按钮，以便在单击第一个按钮时中断 while 循环，并在按下第二个按钮时恢复执行。这可以在不使用线程、多处理或异步性的情况下完成吗？

Answer 1

这是我通过线程包并基于 https://ipywidgets.readthedocs.io/en/latest/examples/Widget%20Asynchronous.html 中给出的后台工作小部件示例得出的答案。 .它肯定没有优化，并且可能不符合良好实践。欢迎任何想出更好答案的人提供。

# importing packages.
import threading
from IPython.display import display
import ipywidgets as widgets
import time

# defining progress bar 'progress', start, stop and resume buttons
# 'start_button', 'stop_button' and 'resume_button', and horizontal
# box 'Hbox'.
progress = widgets.FloatProgress(value=0.0, min=0.0, max=1.0)
start_button = widgets.Button(description="start fill")
stop_button = widgets.Button(description="stop fill/empty")
resume_button = widgets.Button(description="resume fill/empty")
Hbox = widgets.HBox(children=[start_button, stop_button, resume_button, progress])

# defining boolean flags 'pause' and 'resume'.
pause = False
restart = False

# defining 'on_button_clicked_start()' function.
def on_button_clicked_start(b):
    # setting global variables.
    global pause
    global thread
    global restart
    # conditinoal for checking whether the thread is alive;
    # if it isn't, then start it.
    if not thread.is_alive():
        thread.start()
    # else, pause and set 'restart' to True for setting
    # progress bar values to 0.
    else:
        pause = True
        restart = True
        time.sleep(0.1)
        restart = False
    # conditional for changing boolean flag 'pause'.
    if pause:
        pause = not pause
    
# defining 'on_button_clicked_stop()' function.    
def on_button_clicked_stop(b):
    # defining global variables.
    global pause
    # conditional for changing boolean flag 'pause'.
    if not pause:
        pause = not pause
        
# defining 'on_button_clicked_resume()' function.
def on_button_clicked_resume(b):
    # defining global variables.
    global pause
    global restart
    # conditional for changing boolean flags 'pause' and 'restart'
    # if necessary.
    if pause:
        if restart:
            restart = False
        pause = not pause

# call to 'on_button_clicked_start()' function when clicking the button.
start_button.on_click(on_button_clicked_start)
# call to 'on_button_clicked_stop()' function when clicking the button.
stop_button.on_click(on_button_clicked_stop)
# call to 'on_button_clicked_resume()' function when clicking the button.
resume_button.on_click(on_button_clicked_resume)

# defining the 'work()' function.
def work(progress):
    # setting global variables.
    global pause
    i = 0
    i_m1 = 0
    # setting 'total' variable.
    total = 100
    # infinite loop.
    while True:
        # stop/resume conditional.
        if not pause:
            # filling the progress bar.
            if (i == 0) or i > i_m1 and not pause:
                time.sleep(0.1)
                if i == i_m1:
                    pass
                else:
                    i_m1 = i
                i += 1
                progress.value = float(i)/total
            # emptying the progress bar.
            if (i == 101) or i < i_m1 and not pause:
                time.sleep(0.1)
                if i == i_m1:
                    pass
                else:
                    i_m1 = i
                i -= 1
                progress.value = float(i)/total
        else:
            if restart:
                i = 0
                i_m1 = 0

# setting the thread.
thread = threading.Thread(target=work, args=(progress,))
# displaying statement.
display(Hbox)