from tkinter import *

def add_number():
    num = num_box.get()
    if num.isdigit():
        num_list.insert('end', num)
        num_box.delete(0, 'end')
        num_box.focus()
    else:
        num_box.delete(0, 'end')
        num_box.focus()

def clear_list():
    num_list.delete(0, 'end')
    num_box.focus()

window = Tk()
window.title("Lista de Números")
window.geometry("450x200")

label1 = Label(text="Ingresa un número:")
label1.place(x=20, y=20, width=150, height=25)

num_box = Entry()
num_box.place(x=170, y=20, width=100, height=25)
num_box.focus()

button1 = Button(text="Agregar", command=add_number)
button1.place(x=300, y=20, width=100, height=25)

num_list = Listbox()
num_list.place(x=170, y=50, width=100, height=100)

button2 = Button(text="Limpiar", command=clear_list)
button2.place(x=300, y=50, width=100, height=25)

window.mainloop()