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How to pass arguments to a Button command in Tkinter?

Suppose I have the following Button made with Tkinter in Python:

import Tkinter as Tk
win = Tk.Toplevel()
frame = Tk.Frame(master=win).grid(row=1, column=1)
button = Tk.Button(master=frame, text='press', command=action)

The method action is called when I press the button, but what if I wanted to pass some arguments to the method action?

I have tried with the following code:

button = Tk.Button(master=frame, text='press', command=action(someNumber))

This just invokes the method immediately, and pressing the button does nothing.


See Python Argument Binders for standard techniques (not Tkinter-specific) for solving the problem. Working with callbacks in Tkinter (or other GUI frameworks) has some special considerations because the return value from the callback is useless.

If you try to create multiple Buttons in a loop, passing each one different arguments based on the loop counter, you may run into problems due to what is called late binding. Please see tkinter creating buttons in for loop passing command arguments for details.

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Answer

I personally prefer to use lambdas in such a scenario, because imo it’s clearer and simpler and also doesn’t force you to write lots of wrapper methods if you don’t have control over the called method, but that’s certainly a matter of taste.

That’s how you’d do it with a lambda (note there’s also some implementation of currying in the functional module, so you can use that too):

button = Tk.Button(master=frame, text='press', command= lambda: action(someNumber))
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