Outside tkinter I do not know of a way to get and respond to a single keystroke. Inside tkinter the code below does it while providing examples of binding, focus, configure, update, and lots of other stuff.

import tkinter as tk
from tkinter import *
import sys
import time

root=tk.Tk()
root.geometry("1024x768")
msg = StringVar()
msg.set("Keypress Response Demo: press a key, 'Enter' to exit.")

def respond(self):
    # keypress=repr(self.char)
    msg.set("keypress registered! input was: "+ self.char +", ascii: "+ str(ord(self.char)))
    
def ifreturn(self):    
    if int(ord(self.char))==13:
        msg.set("Return/enter keypress dectected.  App closing in 3 seconds")
        root.update()
        time.sleep(2)
        l1.configure(relief='flat')
        root.update
        for i in range(3,0,-1):
            msg.set(str(i))
            root.update()
            time.sleep(1)
        root.destroy()
        sys.exit

l1=tk.Label(takefocus=1, textvariable=msg, font=('Verdana',20,'bold'), pady=330, bd=10, relief='groove')
l1.pack()
l1.bind("<Key>", respond)
l1.bind('<Return>', ifreturn)
l1.focus_set()

root.mainloop()