Combining Tkinter mainloop with another event listener

Question

I am trying to build a program that listens for certain key combinations and then shows information to the user in a Tkinter window. To do this, I'm using a keylogger like so (simplified for this example):

from pyHook import HookManager
from pythoncom import PumpMessages
import Tkinter as tk

def on_keyboard_event(event):
    label.config(text=event.Key)
    root.update()
    return True

hm = HookManager()
hm.KeyDown = on_keyboard_event
hm.HookKeyboard()
root = tk.Tk()
label = tk.Label(root, text='Hello world')
label.pack()
PumpMessages()

As expected, the window pops up and shows the user what key they pressed. However, I would like to integrate functionality to show other messages by interacting with the Tkinter window, such as by pressing a button. However, it seems I need Tkinter's mainloop to do this, which I can't figure out how to run alongside PumpMessages(), since it also halts the code similar to mainloop().

I tried running root.mainloop() in a root.after(), and I tried recreating root.mainloop like so:

def mainloop():
    root.update()
    root.after(50, mainloop)

and then running it right before PumpMessages, but neither of these solutions worked. It also doesn't seem like you can run PumpMessages or root.mainloop in a thread, though I could just not be doing it right. If this is not possible with Tkinter, is there an alternate Python GUI I could use that would make it possible?

Jake · Accepted Answer · 2017-02-08 16:29:40Z

0

You don't need to create a function to use mainloop() so just simply place the mainloop() at the bottom of your code. If you want a delay on it, use root.after(milliseconds, function)

Also, remember to put mainloop() before PumpMessages()

e.g.

def mainloopfunction():
    mainloop()

root.after(5000, mainloopfunction)

Hope I could help!

edited Feb 8, 2017 at 16:29

answered Feb 8, 2017 at 8:17

Jake

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6 Comments

Sam Krygsheld Over a year ago

Unfortunately, this doesn't work. If I put mainloop() at the end, it is never reached because the code never progresses past PumpMessages(). If I use after as displayed here, the interface becomes unresponsive as soon as it starts the mainloop. EDIT - actually, it doesn't appear that it ever reaches the mainloop, so PumpMessages() must be preventing after from executing it's function.

Jake Over a year ago

Have you tried running mainloop before PumpMessages()

Sam Krygsheld Over a year ago

Huh. That does seem to work, though the code never reaches PumpMessages(), so that must not be a necessary part of the keylogger. This doesn't exactly answer the question, but I guess it works.

Sam Krygsheld Over a year ago

After some testing, it appears that PumpMessages (which lacks almost any documentation online) is necessary only if you are not using mainloop. Basically, you need some sort of event listener running to pick up keystrokes, but it doesn't need to be PumpMessages.

Jake Over a year ago

So is that your problem solved or is there still something wrong?

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