PySimpleGUI/DemoPrograms/Demo_Design_Pattern_Persistent_Window.py

import sys

if sys.version_info[0] >= 3:
    import PySimpleGUI as sg
else:
    import PySimpleGUI27 as sg

layout =    [
            [sg.Text('Your typed chars appear here:'), sg.Text('', key='_OUTPUT_')],
            [sg.Input(do_not_clear=True, key='_IN_')],
            [sg.Button('Show'), sg.Button('Exit')]
            ]

window = sg.Window('Window Title').Layout(layout)

while True:  # Event Loop
    event, values = window.Read()
    print(event, values)
    if event is None or event == 'Exit':
        break
    if event == 'Show':
        # change the "output" element to be the value of "input" element  
        window.FindElement('_OUTPUT_').Update(values['_IN_'])

window.Close()