How to get the index of selected option in Tkinter Combobox?

In this article, we will be discussing how to get the index of the selected options in the Tkinter Combobox. 

A Combobox is a combination of a Listbox and an Entry widget. This widget allows users to select one value from a set of values.

Syntax:

def get_index(*arg):
   Label(app, text="The value at index " + str(combo.current()) +\
    " is" + " " + str(var.get()), font=('#Font of Text')).pack()
var = StringVar()
combo = ttk.Combobox(app, textvariable=var)
var.trace('w', get_index)

Stepwise Implementation:

Step 1: First of all, import the library Tkinter.

from tkinter import *
from tkinter import ttk

Step 2: Now, create a GUI app using Tkinter.

app=Tk()

Step 3: Next, set the geometry of the app.

app.geometry("#Dimensions of the app")

Step 4: Further, create a function to clear the Combobox.

def clear():
   combo.set('')

Step 5: Later on, create a function to set the index of the selected option in Combobox.

def get_index(*arg):
  Label(app, text="The value at index " + str(combo.current())\
   + " is" + " " + str(var.get()), font=('#Font of Text')).pack()

Step 6: Moreover, create a tuple of some values to be added in the Combobox.

months = ('January', 'February', 'March', 'April', 'May',
 'June', 'July','August','September','October',
 'November','December')

Step 7: Then, create a Combobox widget and add the values in that Combobox.

var = StringVar()
combo = ttk.Combobox(app, textvariable=var)
combo['values'] = months
combo['state'] = 'readonly'
combo.pack(padx=#x-axis padding value, pady=#y-axis padding value)

Step 8: To a greater extent, set the tracing for the given variable.

var.trace('w', get_index)

Step 9: Furthermore, create a button to clear the selected Combobox text value.

button = Button(app, text="Clear", command=clear)
button.pack()

Step 10: Finally, make an infinite loop for displaying the app on the screen.

app.mainloop()

Example:

Python3

# Python program to get index of selected
# option in Tkinter Combobox

# Import the libraries tkinter
from tkinter import *
from tkinter import ttk

# Create a GUI app
app = Tk()

# Set the geometry of the app
app.geometry("600x400")

# Function to clear the Combobox
def clear():
    combo.set('')

# Function to print the index of selected option
# in Combobox
def get_index(*arg):
    Label(app, text="The value at index " + str(combo.current()) +
          " is" + " " + str(var.get()), font=('Helvetica 12')).pack()


# Define Tuple of months
months = ('January', 'February', 'March', 'April', 'May', 'June',
          'July', 'August', 'September', 'October', 'November',
          'December')

# Create a Combobox widget
var = StringVar()
combo = ttk.Combobox(app, textvariable=var)
combo['values'] = months
combo['state'] = 'readonly'
combo.pack(padx=5, pady=5)

# Set the tracing for the given variable
var.trace('w', get_index)

# Create a button to clear the selected combobox
# text value
button = Button(app, text="Clear", command=clear)
button.pack()

# Make infinite loop for displaying app on
# the screen
app.mainloop()

Output: