close to solution to widget_example_finish_indicator

widget_example_finish_indicator.py

# towards addressing https://discourse.jupyter.org/t/how-to-make-start-and-stop-buttons/8331?u=fomightez
# Paste this into a cell after going to https://github.com/fekad/jupyter-jsmol and pressing `launch binder` to start a session.
# Currently it doesn't update the status text below if you run the process to completion (10 seconds). I tried several ways to trigger that and none seemed to update or add that to `self.putput`
import ipywidgets as widgets
from ipywidgets import Output
from IPython.display import display, Javascript
from traitlets import Unicode, validate
import time
import threading

class Timer():

    def __init__(self,limit=10):
        #self.value = Unicode('00:00:00').tag(sync=True)
        #self.labwidg = widgets.Button(description="Start",layout=lay(120,50))
        self.labwidg = widgets.Button(description="Start")
        self.labwidg.on_click(self.threadTimer)
        #self.labwidgstop =widgets.Button(description="Stop",layout=lay(120,50))
        self.labwidgstop =widgets.Button(description="Stop")
        self.labwidgstop.on_click(self.stopTime)
        self.labwidg.on_click(self.threadTimer)
        self.output = widgets.Output()
        with self.output:
            print("\nProcess status:")
        #self.labwidg.style.button_color = "gree"
        #widgets.Label('00:00:00')
        #display(self.labwidg)
        self.limit = limit
        self.stopTimer = False
        self.thread = None
        self.buttonState = "Start"
    def timeit(self, limit=10):
        #display(self)
        hours = 0
        mins = 0
        secs = 0
        for i in range(1,(limit+1)):
            if i > 9:
                with self.output:
                    print("\nProcess finished")
                self.labwidg.description = 'Finished'
                self.buttonState == "Finished"
                self.thread.stop = True
            if(self.buttonState == "Start"):
                self.labwidg.button_style="primary"
                #self.labwidg.style.font_weight = "50px"
            elif(self.buttonState == "Stop"):
                self.labwidg.button_style="success"
                #self.labwidg.style.font_weight = "50px"
            elif(self.buttonState == "Reset"):
                self.labwidg.button_style="warning"
                #self.labwidg.style.font_weight = "50px"
            if(self.stopTimer):
                self.stopTimer = False
                self.thread = None
                break
            if i%60 == 0:
                if i%3600 == 0:
                    secs = 0
                    mins = 0
                    hours += 1
                else:
                    secs = 0
                    mins += 1
            else:
                secs += 1
            time.sleep(0.5)
            #self.labwidg.description = '{hour:02}:{minute:02}:{second:02}'.format(hour=hours,minute=mins,second=secs)
            self.labwidg.description = f"\rRound {i}"
        self.labwidg.description = 'Finished'
    #def twrap(self,b,limit=180):
    #    self.timeit(limit=limit)
    def threadTimer(self,b):
        #b.description = self.buttonState
        if(self.buttonState == "Start"):
            if(self.thread == None):
                self.thread = threading.Thread(target=self.timeit,args=(self.limit,))
                self.thread.start()
                with self.output:
                    print("\nProcess started")
                self.buttonState = "Stop"
        elif(self.buttonState == "Stop"):
            if(self.thread != None):
                self.stopTimer=True
                self.buttonState = "Reset"
        else:
            self.labwidg.description = 'Start'
            self.Thread = None
            self.stopTimer=False
            self.buttonState = "Start"
    def stopTime(self,b):
        self.stopTimer=True
        with self.output:
            print("\nProcess stopped")


#def startTimer(b,timer):
    #, args=(,))
def lay(width,height):
    return widgets.Layout(width=str(width)+"px",height=str(height)+"px")
def display_timer():
    timer = Timer()
    display(timer.labwidg)
    display(timer.labwidgstop)
    display(timer.output)

display_timer()

There's an example here of a related example of using a button to stop am iterating process in answer to Kill a loop with Button Jupyter Notebook?. It has multiple approaches, including one with multiprocessing.