Question

I’m trying to do Hide/Show for my application with withdraw()/deiconify() in Tkinter, but after deiconify() method call my app hangs. Run this code on Win7.
What do I do wrong?

import Tkinter as tk
import threading


class MyApp(object):
    def __init__(self, parent):
        self.root = parent
        self.root.geometry('400x300')
        self.root.title('My Application')

        btn = tk.Button(parent, text='Hide', command=self.onClick)
        btn.pack()

    def onClick(self):
        self.hide()
        self.t = threading.Timer(3, self.show)
        self.t.start()

    def hide(self):
        print 'hide()'
        print 'state: ', self.root.state()
        print 'withdraw()'
        self.root.withdraw()
        print 'state: ', self.root.state()

    def show(self):
        print 'show()'
        print 'state: ', self.root.state()
        print 'deiconify()'
        self.root.deiconify()
        print 'state: ', self.root.state()
        print 'show end'

if __name__ == '__main__':
    root = tk.Tk()
    app = MyApp(root)
    root.mainloop()

UPD: there is a working sample:

import Tkinter as tk
import sched
import time


class MyApp(object):
    def __init__(self, parent):
        self.root = parent
        self.root.geometry('400x300')

        btn = tk.Button(parent, text='Hide', command=self.onClick)
        btn.pack()

        self.scheduler = sched.scheduler(time.time, time.sleep)

    def onClick(self):
        self.hide()
        self.scheduler.enter(3, 1, self.show, ())
        self.scheduler.run()

    def hide(self):
        self.root.withdraw()

    def show(self):
        self.root.deiconify()

if __name__ == '__main__':
    root = tk.Tk()
    app = MyApp(root)
    root.mainloop()

Answer 1

Tkinter is not thread safe, and you are calling self.root.deiconify() from a thread. That is most likely the source of your problem. You’ll have to re-architect your solution to have the thread use a thread-safe queue to request that the main loop make calls into Tkinter.

There’s a whole lot you can do with Tkinter without using threads. Are you certain you need them?