Hey there! Let's get that button working smoothly. The error you're seeing is a straightforward case-sensitivity issue—super easy to fix once you spot it.

What's Causing the Error? #

Tkinter widget options are case-sensitive, and the correct parameter name for linking a button's click action is lowercase command, not uppercase COMMAND. When you use COMMAND=btn_clicked, Tkinter doesn't recognize it as a valid button option, which throws the "Unknown option -command" message.

Corrected Code #

Here's your code with the fix applied:

from tkinter import *
root = Tk()
e = Entry(root, width=20)
e.grid(row=0, column=0)

def btn_clicked():
    label = Label(root, text=f"Hello {e.get()}!")
    label.grid(row=1, column=0)

# Changed uppercase COMMAND to lowercase command
button = Button(root, padx=10, text="Click this", command=btn_clicked)
button.grid(row=0, column=1)

root.mainloop()

Quick Optimization Tip #

Right now, every button click creates a new Label that stacks on top of the old ones. For a cleaner interface, you can initialize a single label once and update its text instead:

from tkinter import *
root = Tk()
e = Entry(root, width=20)
e.grid(row=0, column=0)

# Initialize an empty label upfront
result_label = Label(root, text="")
result_label.grid(row=1, column=0)

def btn_clicked():
    # Update the existing label's text instead of making a new one
    result_label.config(text=f"Hello {e.get()}!")

button = Button(root, padx=10, text="Click this", command=btn_clicked)
button.grid(row=0, column=1)

root.mainloop()

内容的提问来源于stack exchange，提问作者ihsan