How do I change the value of a label dynamically depending on a ComboBox in CustomKinter?

This is my first time using CustomKinter to make a simple GUI. I am trying to get the value of a customtkinter label to change depending on the value selected by the combobox. The textvariable for the output should change for the values in the calculate_output function; the output label is not changing.

from tkinter import StringVar

import customtkinter as ctk

root = ctk.CTk()
root.title("Window")
root.geometry("400x300")

label_1 = ctk.CTkLabel(root, text="Value:", font=("Frutiger", 21))
label_1.place(x=100, y=100)

values = ["80", "150", "180", "250"]

drop_down = ctk.CTkComboBox(root, values=values, border_color="#0072CE", font=("Frutiger", 21),
                            button_color="#005EB8")
drop_down.place(x=220, y=100)

output_var = StringVar()

label_2 = ctk.CTkLabel(root, text="Output:", font=("Frutiger", 21))
label_2.place(x=100, y=200)

output = ctk.CTkLabel(root, font=("Frutiger", 21), textvariable=output_var)
output.place(x=200, y=200)


def calculate_output(event):
    drop_value = drop_down.get()
    try:
        if drop_value == "80":
            output_var.set("None")
        elif drop_value == "150":
            output_var.set("Aluminium")
        elif drop_value == "180":
            output_var.set("Copper")
        elif drop_value == "250":
            output_var.set("Tin")
    except ValueError:
        output_var.set("Invalid input")


drop_down.bind("<<ComboboxSelected>>", calculate_output)

root.mainloop()

enter image description here

I tried editting the function and binding but I have no idea where the issue is. Help would be appreciated.

Solution

You can use the command parameter of the CTkComboBox to link it to your function as such:

drop_down = ctk.CTkComboBox(root, values=values, border_color="#0072CE", font=("Frutiger", 21), button_color="#005EB8", command=calculate_output)

That way the function will be executed every time you select a new value. Also make sure to define the function before you link it to the combobox. Your final code would look like this:

from tkinter import StringVar

import customtkinter as ctk

root = ctk.CTk()
root.title("Window")
root.geometry("400x300")

label_1 = ctk.CTkLabel(root, text="Value:", font=("Frutiger", 21))
label_1.place(x=100, y=100)

values = ["80", "150", "180", "250"]

output_var = StringVar()

label_2 = ctk.CTkLabel(root, text="Output:", font=("Frutiger", 21))
label_2.place(x=100, y=200)

output = ctk.CTkLabel(root, font=("Frutiger", 21), textvariable=output_var)
output.place(x=200, y=200)


def calculate_output(event):
    drop_value = drop_down.get()
    try:
        if drop_value == "80":
            output_var.set("None")
        elif drop_value == "150":
            output_var.set("Aluminium")
        elif drop_value == "180":
            output_var.set("Copper")
        elif drop_value == "250":
            output_var.set("Tin")
    except ValueError:
        output_var.set("Invalid input")

drop_down = ctk.CTkComboBox(root, values=values, border_color="#0072CE", font=("Frutiger", 21),
                            button_color="#005EB8", command=calculate_output)
drop_down.place(x=220, y=100)

root.mainloop()