tkinter window not opening?

Question

Python

from tkinter import *

def printer(event):
    print ("Hello")

root = Tk()
but = Button(root)
but["text"] = "Печать"
but.bind("<Button-1>",printer)

but.pack()
root.mainloop

I'm just starting to learn tkinter and here's the thing.

Answer 1

root.mainloop ()