在Ipywidgets中为持续循环添加停止/恢复按钮（无需多线程等）

Absolutely! You can implement stop/resume functionality by using a simple flag variable to control the execution flow of your loops. Since we're working in a synchronous context, we just need to check this flag at regular intervals within the work function to pause or resume progress.

Key Changes: #

• Add a boolean flag is_running to track whether the progress bar should be updating
• Modify the work() function to check this flag before each progress update; if paused, wait in a low-impact loop until the flag is re-enabled
• Add Stop and Resume buttons, with callbacks to toggle the is_running flag

Full Modified Code #

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

# Control flag to manage execution state
is_running = True

# Create widgets
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", button_style="danger")
resume_button = widgets.Button(description="Resume", button_style="success")
Hbox = widgets.HBox(children=[start_button, stop_button, resume_button, progress])

def on_button_clicked_start(b, progress):
    global is_running
    is_running = True
    work(progress)

def on_button_clicked_stop(b):
    global is_running
    is_running = False

def on_button_clicked_resume(b):
    global is_running
    is_running = True

# Bind button callbacks
start_button.on_click(functools.partial(on_button_clicked_start, progress=progress))
stop_button.on_click(on_button_clicked_stop)
resume_button.on_click(on_button_clicked_resume)

def work(progress):
    total = 100
    i = 0
    while True:
        # Fill progress bar
        while progress.value < 1.0 and is_running:
            time.sleep(0.01)
            i += 1
            progress.value = float(i)/total
            # Wait if paused mid-fill
            while not is_running:
                time.sleep(0.01)
        
        # Empty progress bar
        while progress.value > 0.0 and is_running:
            time.sleep(0.01)
            i -= 1
            progress.value = float(i)/total
            # Wait if paused mid-empty
            while not is_running:
                time.sleep(0.01)

display(Hbox)

How It Works: #

• The is_running flag acts as a toggle: when set to False, the work function pauses its progress updates and waits in a low-impact loop (with small time.sleep() calls to avoid hogging resources)
• Clicking "Stop" sets is_running to False, which triggers the waiting loop in the current progress stage
• Clicking "Resume" sets is_running back to True, allowing the progress bar to continue from where it left off
• The "Start" button re-enables the flag and starts the cycle if it was stopped

This approach keeps everything in a single synchronous thread, avoiding the complexity of concurrency while still giving you full control over the progress execution.

内容的提问来源于stack exchange，提问作者AZarketa