Python3: function call from pressing tkinter.button

Question

Please note that this is written in python 3

I am using Tkinter and am trying to call the foo-function by pressing the button in the tk-window and get "Hello World!" printed, what am I doing wrong?

from tkinter import *
window1 = Tk()

class WidgetCreate(object):

    def __init__(self, widget_type, window_num, text_str, fun, numr, numc):
        self.obj = Button(window_num, text=text_str, command=lambda: fun)
        self.obj.grid(row=numr, column=numc)

def foo():
    print("Hello World!")       

but1 = WidgetCreate("Button", window1, "This Button 1", foo, 1, 1)

window1.mainloop()

The button is visible in the to-window however when pressed nothing happens :(

If an answer solves your problem, it would be nice if you mark it as accepted. — TobiMarg
– TobiMarg, Commented Jun 30, 2014 at 16:18
The delay is no problem. Thanks, I commented only because you could have forgotten / not found it as new user. :) — TobiMarg
– TobiMarg, Commented Jun 30, 2014 at 17:10

TobiMarg · Accepted Answer · 2014-06-30 16:13:38Z

2

You miss the parenthesis in your command argument to Button. So your lambda function doesn't call the function you want. It has to be:

self.obj = Button(window_num, text=text_str, command=lambda: fun())

Or even simpler you do it without the lambda function and give fun directly as argument:

self.obj = Button(window_num, text=text_str, command=fun)

edited Jun 30, 2014 at 16:13

answered Jun 30, 2014 at 16:08

TobiMarg

3,8471 gold badge22 silver badges25 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Christian Abdelmassih Over a year ago

That little error took me 2 whole hours to notice. Thank you!

TobiMarg Over a year ago

It's even better if you use the second way, because the lambda thing is not necessary.

Adam Smith Over a year ago

Typically you'll only need a lambda if you have to pass arguments to a function. If you had to tell foo what to print, you'd have to do command=lambda: fun("Hello, world!") but if you can just call the function then there's no reason to wrap it inside another function :)

Collectives™ on Stack Overflow

Python3: function call from pressing tkinter.button

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related