OK, now one main block only , but loop.run_forever() ? idk...

[Wu Xi]

from tkinter import *                                    #    I cant see anything wrong with the async_loop business here. It works like a charm.
from tkinter import messagebox                           #    is there a serious concern doing things his way ? 
import asyncio , threading ,  random                     #    goal is multi tasking with the GUI not freezing before loop completed
                                                         #    which is being achieved here !    works in py 3.7 of 2018
def _asyncio_thread(async_loop):
    async_loop.run_until_complete(do_urls())

def do_work(async_loop):
    """ Button-Event-Handler starting stuff """
    threading.Thread(target=_asyncio_thread, args=(async_loop,)).start()

async def one_url(url):
    """ One task. """
    global root
    sec = random.randint(1, 8)
    root.update()                                         # more often   
    await asyncio.sleep(sec  )
    return 'url: {}  ---  sec: {}'.format(url, sec)

async def do_urls():
    """ Creating and starting 10 tasks.         """
    tasks   = [one_url(url)  for url  in range(10)]
    completed, pending =  await asyncio.wait(tasks)
    results = [task.result() for task in completed]
    print('\n'.join(results))

def do_notfreeze():  messagebox.showinfo(message='see, Tkinter is still responsive')



if __name__ == '__main__':
    global root
    async_loop = asyncio.get_event_loop()    #  all in this loop
 
    root = Tk()
    Button(master=root, text='do work',       command= lambda:do_work( async_loop )).pack()
    Button(master=root, text='Frozen?',       command= do_notfreeze                ).pack()
    root.update()                                           
    #async_loop.run_forever()             #  <----  uncomment, then it won"t work anymore
    root.mainloop() # how to replace ? 
   
    
  # To do everything in the main thread, 
  # one can replace 'root.mainloop' with loop.run_forever (in the main thread) 
  # and repeated root.update calls.