Copy these design patterns!

All of your PySimpleGUI programs will utilize one of these 2 design patterns depending on the type of window you're implementing.

Beginning in release 4.19.0 the constant WIN_CLOSED replaced using None as the event signaling that a window was closed.

Pattern 1 A - "One-shot Window" - Read a window one time then close it

This will be the most common pattern you'll follow if you are not using an "event loop" (not reading the window multiple times). The window is read and closed.

The input fields in your window will be returned to you as a dictionary (syntactically it looks just like a list lookup)

import PySimpleGUI as sg

sg.theme('Dark Blue 3')  # please make your windows colorful

layout = [[sg.Text('SHA-1 and SHA-256 Hashes for the file')],
                 [sg.InputText(), sg.FileBrowse()],
                 [sg.Submit(), sg.Cancel()]]

window = sg.Window('SHA-1 & 256 Hash', layout)

event, values = window.read()
window.close()

source_filename = values[0]     # the first input element is values[0]

Pattern 1 B - "One-shot Window" - Read a window one time then close it (compact format)

Same as Pattern 1, but done in a highly compact way. This example uses the close parameter in window.read to automatically close the window as part of the read operation (new in version 4.16.0). This enables you to write a single line of code that will create, display, gather input and close a window. It's really powerful stuff!

import PySimpleGUI as sg

sg.theme('Dark Blue 3')  # please make your windows colorful

event, values  = sg.Window('SHA-1 & 256 Hash', [[sg.Text('SHA-1 and SHA-256 Hashes for the file')],
                        [sg.InputText(), sg.FileBrowse()],
                        [sg.Submit(), sg.Cancel()]]).read(close=True)

source_filename = values[0]     # the first input element is values[0]

Pattern 2 A - Persistent window (multiple reads using an event loop)

Some of the more advanced programs operate with the window remaining visible on the screen. Input values are collected, but rather than closing the window, it is kept visible acting as a way to both output information to the user and gather input data.

This code will present a window and will print values until the user clicks the exit button or closes window using an X.

import PySimpleGUI as sg

sg.theme('Dark Blue 3')  # please make your windows colorful

layout = [[sg.Text('Persistent window')],
          [sg.Input()],
          [sg.Button('Read'), sg.Exit()]]

window = sg.Window('Window that stays open', layout)

while True:
    event, values = window.read()
    if event == sg.WIN_CLOSED or event == 'Exit':
        break
    print(event, values)

window.close()

Pattern 2 B - Persistent window (multiple reads using an event loop + updates data in window)

This is a slightly more complex, but maybe more realistic version that reads input from the user and displays that input as text in the window. Your program is likely to be doing both of those activities (input and output) so this will give you a big jump-start.

Do not worry yet what all of these statements mean. Just copy it so you can begin to play with it, make some changes. Experiment to see how thing work.

This example introduces the concept of "keys". Keys are super important in PySimpleGUI as they enable you to identify and work with Elements using names you want to use. Keys can be (almost) ANYTHING, except None or a List (a tuple is fine). To access an input element's data that is read in the example below, you will use values['-IN-'] instead of values[0] like before.

import PySimpleGUI as sg

sg.theme('Dark Blue 3')  # please make your windows colorful

layout = [[sg.Text('Your typed chars appear here:'), sg.Text(size=(12,1), key='-OUTPUT-')],
          [sg.Input(key='-IN-')],
          [sg.Button('Show'), sg.Button('Exit')]]

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

while True:  # Event Loop
    event, values = window.read()
    print(event, values)
    if event == sg.WIN_CLOSED or event == 'Exit':
        break
    if event == 'Show':
        # change the "output" element to be the value of "input" element
        window['-OUTPUT-'].update(values['-IN-'])

window.close()