tkinter: how to use after method
Solution 1
You need to give a function to be called after the time delay as the second argument to after
:
after(delay_ms, callback=None, *args)
Registers an alarm callback that is called after a given time.
So what you really want to do is this:
tiles_letter = ['a', 'b', 'c', 'd', 'e']
def add_letter():
rand = random.choice(tiles_letter)
tile_frame = Label(frame, text=rand)
tile_frame.pack()
root.after(500, add_letter)
tiles_letter.remove(rand) # remove that tile from list of tiles
root.after(0, add_letter) # add_letter will run as soon as the mainloop starts.
root.mainloop()
You also need to schedule the function to be called again by repeating the call to after
inside the callback function, since after
only executes the given function once. This is also noted in the documentation:
The callback is only called once for each call to this method. To keep calling the callback, you need to reregister the callback inside itself
Note that your example will throw an exception as soon as you've exhausted all the entries in tiles_letter
, so you need to change your logic to handle that case whichever way you want. The simplest thing would be to add a check at the beginning of add_letter
to make sure the list isn't empty, and just return
if it is:
def add_letter():
if not tiles_letter:
return
rand = random.choice(tiles_letter)
tile_frame = Label(frame, text=rand)
tile_frame.pack()
root.after(500, add_letter)
tiles_letter.remove(rand) # remove that tile from list of tiles
Live-Demo: repl.it
Solution 2
I believe, the 500ms run in the background, while the rest of the code continues to execute and empties the list.
Then after 500ms nothing happens, as no function-call is implemented in the after-callup (same as frame.after(500, function=None)
)
user2456977
Updated on July 05, 2022Comments
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user2456977 almost 2 years
Hey I am new to python and am using tkinter for my gui. I am having trouble using the "after" method. The goal is to make a random letter appear every 5 seconds.
Here is my code:
import random import time from tkinter import * root = Tk() w = Label(root, text="GAME") w.pack() frame = Frame(root, width=300, height=300) frame.pack() L1 = Label(root, text="User Name") L1.pack(side=LEFT) E1 = Entry(root, bd =5) E1.pack(side=LEFT) tiles_letter = ['a', 'b', 'c', 'd', 'e'] while len(tiles_letter) > 0: rand = random.choice(tiles_letter) tile_frame = Label(frame, text=rand) tile_frame.pack() frame.after(500) tiles_letter.remove(rand) # remove that tile from list of tiles root.mainloop()
can someone please help me --- the problem is definitely frame.after(500): i'm not sure if it is correct to use "frame" and I don't know what which argument follows the 500.
Thanks
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Russell Smith about 7 yearsYou don't need to use
after
to call it the first time, especially if you doafter(0, ...)
.