tkinter and time.sleep

Question

I am trying to delete text inside a text box after waiting 5 seconds, but instead the program wont run and does sleep over everything else. Also is there a way for me to just make my textbox sleep so i can run other code while the text is frozen?

from time import time, sleep
from Tkinter import *

def empty_textbox():
    textbox.insert(END, 'This is a test')
    sleep(5)
    textbox.delete("1.0", END)

root = Tk()

frame = Frame(root, width=300, height=100)
textbox = Text(frame)

frame.pack_propagate(0)
frame.pack()
textbox.pack()

empty_textbox()

root.mainloop()

Lundeen

Answer 1

You really should be using something like the Tkinter after method rather than time.sleep(...).

There's an example of using the after method at this other stackoverflow question.

Here's a modified version of your script that uses the after method:

from time import time, sleep
from Tkinter import *

def empty_textbox():
    textbox.delete("1.0", END)

root = Tk()

frame = Frame(root, width=300, height=100)
textbox = Text(frame)

frame.pack_propagate(0)
frame.pack()
textbox.pack()

textbox.insert(END, 'This is a test')
textbox.after(5000, empty_textbox)

root.mainloop()

Coronation

Answer 2

You can emulate time.sleep in tkinter. For this we still need to use the .after method to run our code alongside the mainloop, but we could add readability to our code with a sleep function. To add the desired behavior, tkinter provides another underestimated feature, wait_variable. wait_variable stops the codeblock till the variable is set and thus can be scheduled with after.

def tksleep(t):
    'emulating time.sleep(seconds)'
    ms = int(t*1000)
    root = tk._get_default_root('sleep')
    var = tk.IntVar(root)
    root.after(ms, var.set, 1)
    root.wait_variable(var)

Real world examples:

• update a Label to display a clock while-loop
• animated writing nested for-loops

Limitation:

• tkinter does not quit while tksleep is used.
  • Make sure there is no pending tksleep by exiting the application.
• Using tksleep casually can lead to unintended behavior

---

UPDATE

TheLizzard worked out something superior to the code above here. Instead of tkwait command he uses the mainloop and this overcomes the bug of not quitting the process as described above, but still can lead to unintended output, depending on what you expect:

import tkinter as tk

def tksleep(self, time:float) -> None:
    """
    Emulating `time.sleep(seconds)`
    Created by TheLizzard, inspired by Thingamabobs
    """
    self.after(int(time*1000), self.quit)
    self.mainloop()
tk.Misc.tksleep = tksleep

# Example
root = tk.Tk()
root.tksleep(2)

Gillmore

So, in the update section, you have to create a new tk.Tk() every time to use the tksleep method? And doesn't the mainloop of that new tk.Tk() instance still block the whole execution? If not, why? Doesn't it all use the normal single thread? – Blate