Python - Change button state based on multiple widgets

userWhUl1 0
Viewed 24

I am trying to change the state of a button based on the user input of two other widgets contained in my program. Ideally I would like the button to change state any time one/both of the widgets values is missing and only be enabled when both values are present. I'm unsure of how to go about doing this. I have tried writing a function to check the value of the two widgets control variables and configure the button accordingly, but with no luck. If any other information is needed for clarity/context, please let me know. Thank you in advance.

import tkinter as tk
from tkinter import ttk

results = dict()  # holds control vars
categories = ['a', 'b', 'c']  # options for combobox


def change_state():

    c = results['category'].get()
    n = results['number_of_recipes'].get()

    if c and n != 0:
        button.configure(state=tk.NORMAL)

    else:
        button.configure(state=tk.DISABLED)


root = tk.Tk()

results['category'] = tk.StringVar()

ttk.Combobox(
    root,
    textvariable=results['category'],
    values=categories,
    justify='right'
).grid(
    column=0,
    row=0
)

results['number_of_recipes'] = tk.IntVar()

ttk.Spinbox(
    root,
    textvariable=results['number_of_recipes'],
    from_=1, to=20, increment=1,
    justify='right',
).grid(
    column=1,
    row=0
)

button = ttk.Button(
    root,
    text='Button',
    state=tk.DISABLED
)

change_state()

button.grid(
    column=2,
    row=0
)

root.mainloop()
tkinter-button tkinter python-3.x python
1 Answers

Use the trace method for the StringVar and IntVar, and bind it to the change_state function.

Then the change_state function will execute whenever either of the widgets values changes and it can set the button to be enabled or disabled accordingly.

For example:

import tkinter as tk
from tkinter import ttk

results = dict()  # holds control vars
categories = ['a', 'b', 'c']  # options for combobox

def change_state(*_):  # <--- now accepts *args
    c = results['category'].get()
    n = results['number_of_recipes'].get()

    if c and n != 0:
        button.configure(state=tk.NORMAL)

    else:
        button.configure(state=tk.DISABLED)

root = tk.Tk()

results['category'] = tk.StringVar()
results['category'].trace('w', change_state)  # <---- added this


ttk.Combobox(
    root,
    textvariable=results['category'],
    values=categories,
    justify='right',
).grid(
    column=0,
    row=0
)

results['number_of_recipes'] = tk.IntVar()
results['number_of_recipes'].trace('w', change_state)  # <-- added this

ttk.Spinbox(
    root,
    textvariable=results['number_of_recipes'],
    from_=1, to=20, increment=1,
    justify='right',
).grid(
    column=1,
    row=0
)

button = ttk.Button(
    root,
    text='Button',
    state=tk.DISABLED
)
button.grid(
    column=2,
    row=0
)

root.mainloop()
userphOc10
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