from tkinter import *
from tkinter import messagebox
root = Tk()


def ok():
    name = s1_wert.get()
    return messagebox.showinfo( f"", name) 


Label(root, text="S = Schere, R = Stein, P = Papier ").pack()

s1_wert = Entry(root)
s1_wert.pack()

Button(root, text="Wählen", command=ok).pack()

    
root.mainloop()