[Python] How to use a <ComboboxSelected> virtual event with tkinter

I am using a tkk.Combobox themed widget in Python 3.5.2. I want an action to happen when a value is selected.

In the Python docs, it says:

The combobox widgets generates a <<ComboboxSelected>> virtual event when the user selects an element from the list of values.
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Here on the Stack, there are a number of answers (1, 2, etc) that show how to bind the event:

cbox.bind("<<ComboboxSelected>>", function)


However, I can't make it work. Here's a very simple example demonstrating my non-functioning attempt:

import tkinter as tk
from tkinter import ttk

tkwindow = tk.Tk()

cbox = ttk.Combobox(tkwindow, values=[1,2,3], state='readonly')
cbox.grid(column=0, row=0)

cbox.bind("<<ComboboxSelected>>", print("Selected!"))

tkwindow.mainloop()


I get one instance of "Selected!" immediately when I run this code, even without clicking anything. But nothing happens when I actually select something in the combobox.

I'm using IDLE in Windows 7, in case it makes a difference.

What am I missing?

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