Python 3 Tkinter : Greet user

main.py

# coding: utf-8
 
from tkinter import Tk, Label, Entry, Button
from tkinter.messagebox import showinfo, showerror

def greet(name):
    if len(name) > 0 :
        showinfo(title="", message="Bonjour  {} !".format(name))
    else :
        showerror(title="Aucun nom", message="Aucun prénom renseigné")

window = Tk()

name_label = Label(window, text="Votre prénom: ")
name_entry = Entry(window, width=20)
validate_button = Button(window, text="Valider", command=lambda : greet(name_entry.get()))

name_label.grid(row=0, column=0)
name_entry.grid(row=0, column=1)
validate_button.grid(row=1, column=1)

window.mainloop()