How to change a buttons state from disabled to active when an option is selected in an OptionMenu Tkinter

Question

I'm trying to change the button state when an option is selected in the option menu, but nothing is changing. Can anyone tell me what I'm doing wrong?

from tkinter import *

def setLabel():
    changed.set("Active")
    
def changeState():
    pick = choose.get()
    if (pick == "op2"):
        button['state'] = button.ACTIVE
        button.config(text = "ACTIVE")
    else:
        button['state'] = app.DISABLED
        button.config(text = "Disabled")

app = Tk()
app.resizable(40,40)

choose = StringVar()
choose.set("op1")
options = OptionMenu(app, choose, "op1", "op2")
options.pack()


button = Button(app, text = "Disabled", state = DISABLED, command = setLabel)
button.pack()

changed = StringVar()
label = Label(app, textvariable = changed, font = ("helvetica", 10))
label.pack()

app.mainloop()

Ah thanks for your help. I only just saw this after I had posted I had figured it out. Thanks again! — ImpulsePenny, Sep 25 '20 at 11:09

Delrius Euphoria · Accepted Answer · 2020-09-25T12:20:26.100

Change your function to this:

def changeState():
    pick = choose.get()
    if (pick == "op2"):
        button['state'] = ACTIVE #means active state
        button.config(text = "ACTIVE")
    else:
        button['state'] = DISABLED #means disabled state
        button.config(text = "Disabled")

Also your not calling your function, so to call it and make the effect active, add a command argument onto your optionmenu, like:

options = OptionMenu(app, choose, "op1", "op2",command=lambda _:changeState())

Using lambda _: because optionmenu command expect a tkinter variable to be passed on, so as to avoid that. You could also have a parameter for your function, but if your calling your function somewhere else, your gonna have to pass in a argument or your could also use parameter like point=None and get rid of the lambda.

Hope this cleared the errors, do let me know if any doubts.

Cheers

ImpulsePenny · Answer 2 · 2020-09-30T09:09:28.353

0

Got it!

Edit: I changed line 9 slightly, removing button.active and replacing with NORMAL and this worked.

from tkinter import *

def setLabel():
    changed.set("Active")
    
def changeState(*args):
    pick = choose.get()
    if (pick == "op2"):
        button['state'] = NORMAL
        button.config(text = "ACTIVE")
    else:
        button['state'] = DISABLED
        button.config(text = "Disabled")

app = Tk()
app.resizable(40,40)

choose = StringVar()
choose.set("op1")
options = OptionMenu(app, choose, "op1", "op2")
choose.trace("w", changeState)
options.pack()


button = Button(app, text = "Disabled", state = DISABLED, command = setLabel)
button.pack()

changed = StringVar()
label = Label(app, textvariable = changed, font = ("helvetica", 10))
label.pack()

app.mainloop()

edited Sep 30 '20 at 09:09

answered Sep 25 '20 at 11:08

ImpulsePenny

1
3

Code-only answers are discouraged here. Please [edit] it and say what you did to fix the problem. – martineau Sep 25 '20 at 11:12
It's a code-only answer to your own question, but you have said what you "got" or what's different from the code in your question — so it makes it less enlightening to others. – martineau Sep 25 '20 at 11:41

score 0 · Answer 3 · answered Sep 25 '20 at 11:35

0

You can add command=changeState in OptionMenu(...) to call changeState() whenever the options is changed:

def changeState(pick):
    if pick == "op2":
        button['state'] = ACTIVE
        button.config(text = "ACTIVE")
    else:
        button['state'] = DISABLED
        button.config(text = "Disabled")

...

options = OptionMenu(app, choose, "op1", "op2", command=changeState)

answered Sep 25 '20 at 11:35

acw1668

40,144
5
22
34

Hmmm, the command of optionmenu takes an argument of the tkinter variable right? So this will produce error. You might want to use lambda – Delrius Euphoria Sep 25 '20 at 12:03
@CoolCloud Did you try it? The callback will be passed the selected item. – acw1668 Sep 25 '20 at 12:09
Actually i did and got the error - Check [here](https://stackoverflow.com/questions/35974203/optionmenu-command-function-requires-argument) – Delrius Euphoria Sep 25 '20 at 12:11
1

@CoolCloud My version of `changeState()` has an argument, so it is the same as what you said `lambda _`. So I don't know why you propose to use lambda. – acw1668 Sep 25 '20 at 12:17
Oh i dint notice that the parameter, yes your correct. – Delrius Euphoria Sep 25 '20 at 12:18

How to change a buttons state from disabled to active when an option is selected in an OptionMenu Tkinter

3 Answers3