Using .config in tkinter

问题

Beginner here Having trouble getting a label to update on a simple countdown app, Can anyone explain why the label does not update in the loop?

import time
import tkinter as tk

root = tk.Tk()
root.geometry('150x100')

seconds_inp = tk.Entry(root)
global time_label
time_label = tk.Label(root, text = '00', font = 20)
start_button = tk.Button(root, text = 'start', command = lambda: countdown_clock(int(seconds_inp.get())))
def countdown_clock(seconds):
    while True:
        seconds = seconds - 1
        time.sleep(1)
        time_label.config(text = seconds)


        print(seconds)
        if seconds == 0:
            time_label.config(text = 'time!')
            break



time_label.grid(row = 1, column = 0)
start_button.grid(row = 2, column = 0)
seconds_inp.grid(row = 3, column = 0)
root.mainloop()

回答1:

while loops, leads to windows being unresponsive after sometime, so the best way is to get rid of that and use the inbuilt, after() method.

Here is a working example:

import time
import tkinter as tk

root = tk.Tk()
root.geometry('150x100')

seconds_inp = tk.Entry(root)

time_label = tk.Label(root, text='00', font=20)
start_button = tk.Button(
    root, text='start', command=lambda: countdown_clock(int(seconds_inp.get())))


def countdown_clock(seconds):
    seconds = seconds - 1
    time_label.config(text=seconds)
    call = root.after(1000, lambda: countdown_clock(seconds))
    if seconds == 0:
        root.after_cancel(call)
        time_label.config(text='Time up!!')
    print(seconds)


time_label.grid(row=1, column=0)
start_button.grid(row=2, column=0)
seconds_inp.grid(row=3, column=0)
root.mainloop()

All i did was,I removed the while because it will interrupt the mainloop() method, so then i used after() method to call the function continuously till second reaches 0, and then i cancel the after() and finally update the label. And i removed global outside the functions as those are pointless to be called outside functions.

Hope this cleared your doubt.

Cheers

回答2:

Use after instead of while and wait. Also, you were subtracting a second as soon as your clock begins. Send the subtracted value to the next call instead. If all you are going to do is stick every widget on the next row in one column then you don't have to be specific in grid(), you just have to make sure you call grid on the widgets in the proper order. If you add more columns the rules change back to how you were doing it.

import time
import tkinter as tk

root = tk.Tk()
root.geometry('150x100')

def countdown_clock(s, t):
    if not s:
        t.configure(text='time!')
        return
    
    t.configure(text=s)
    root.after(1000, lambda: countdown_clock(s-1, t))
    


time_lbl     = tk.Label(root, text='00', font=20)
time_lbl.grid()

start_btn    = tk.Button(root, text='start', command=lambda: countdown_clock(int(seconds_ent.get()), time_lbl))
start_btn.grid()

seconds_ent  = tk.Entry(root)
seconds_ent.grid()

root.mainloop()

来源：https://stackoverflow.com/questions/63779131/using-config-in-tkinter

标签

python

user-interface

tkinter