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POTkinter nested mainloop
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copied!<p>I am writing a videoplayer with <strong>tkinter/python</strong>, so basically I have a GUI that can play a video. Now, I would like to implement a stop button, meaning that I would have a <code>mainloop()</code> for the GUI, and another nested <code>mainloop()</code> to play/stop the video and return to the GUI startup window. <a href="http://www.pythonware.com/library/tkinter/introduction/x9374-event-processing.htm" rel="nofollow">Here</a>, it is said:</p> <blockquote> <p>Event loops can be nested; it's ok to call mainloop from within an event handler.</p> </blockquote> <p>However, I do not understand how to implement this nesting. Can someone please provide me with a simple example of such a script?</p> <h2>EDIT</h2> <p>Here is a working version of my code, since it seems that I am doing something exotic. Of course, I am a newbie, so it may be that I am mistaken about the necessity to have a nested mainloop.</p> <pre><code>#!/usr/bin/python import numpy as np from multiprocessing import Process, Queue import cv2 import cv2.cv as cv from PIL import Image, ImageTk import Tkinter as tk def image_capture(queue): vidFile = cv2.VideoCapture(0) while True: flag, frame=vidFile.read() frame = cv2.cvtColor(frame,cv2.cv.CV_BGR2RGB) queue.put(frame) cv2.waitKey(10) def update_all(root, imagelabel, queue, process, var): if var.get()==True: im = queue.get() a = Image.fromarray(im) b = ImageTk.PhotoImage(image=a) imagelabel.configure(image=b) imagelabel._image_cache = b # avoid garbage collection root.update() root.after(0, func=lambda: update_all(root, imagelabel, queue, process, var)) else: print var.get() root.quit() def playvideo(root, imagelabel, queue, var): print 'beginning' p = Process(target=image_capture, args=(task,)) p.start() update_all(root, imagelabel, queue, p, var) print 'entering nested mainloop' root.mainloop() p.terminate() if var.get()==False: im = ImageTk.PhotoImage(file='logo.png') imagelabel.configure(image=im) imagelabel._image_cache = im # avoid garbage collection root.update() var.set(True) print 'finishing' if __name__ == '__main__': #initialize multiprocessing task = Queue() #GUI of root window root = tk.Tk() #the image container image_label = tk.Label(master=root) image_label.grid(column=0, row=0, columnspan=2, rowspan=1) #fill label with image until video is loaded bg_im = ImageTk.PhotoImage(file='logo.png') image_label['image'] = bg_im #frame for buttons button_frame = tk.Frame(root) button_frame.grid(column=0, row=1, columnspan=1) #load video button and a switch to wait for the videopath to be chosen load_button = tk.Button(master=button_frame, text='Load video',command=lambda: playvideo(root, image_label, task, switch)) load_button.grid(column=0, row=0, sticky='ew') #Stop button switch = tk.BooleanVar(master=root, value=True, name='switch') stop_button = tk.Button(master=button_frame, text='Stop',command=lambda: switch.set(False)) stop_button.grid(column=0, row=1, sticky='ew') #quit button quit_button = tk.Button(master=button_frame, text='Quit',command=root.destroy) quit_button.grid(column=0, row=2, sticky='ew') root.mainloop() </code></pre>

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