New Demo - how to "reuse" a layout (but not by actually reusing it)

DemoPrograms/Demo_Layout_Reuse_Effect.py

@@ -0,0 +1,67 @@
+import PySimpleGUI as sg
+
+"""
+    Demo - Layout "Reuse" (but NOT reusing the layout)
+    As cautioned in the PySimpleGUI documentation, layouts cannot be "reused".
+    
+    That said, there is a very simple design pattern that you'll find in many many
+    Demo Programs.  Any program that is capable of changing the theme uses this
+    same kind of pattern.
+    
+    Goal - write the layout code once and then use it multiple times
+        The layout is reused 
+    
+    Solution - create the layout and window in a function and return it
+
+    Copyright 2021 PySimpleGUI
+"""
+
+
+def make_window():
+    """
+    Defines the layout and creates the window.
+
+    This will allow you to "reuse" the layout.
+    Of course, the layout isn't reused, it is creating a new copy of the layout
+    every time the function is called.
+
+    :return: newly created window
+    :rtype: sg.Window
+    """
+
+    # ------------------- Layout Definition -------------------
+    layout = [[sg.Text('This is your layout')],
+              [sg.Input(key='-IN-')],
+              [sg.Text('You typed:'), sg.Text(size=(20,1), key='-OUT-')],
+              [sg.Button('Go'), sg.Button('Dark Gray 13 Theme'), sg.Button('Exit')]]
+
+    # ------------------- Window Creation -------------------
+    return sg.Window('Window Title', layout)
+
+def main():
+    """
+    Your main program that contains your event loop
+    Rather than creating the layout and Window in this function, you will
+    instead call the make_window function to make the layout and Window
+    """
+
+    window = make_window()      # create the window
+
+    while True:
+        event, values = window.read()
+        print(event, values)
+        if event == sg.WIN_CLOSED or event == 'Exit':
+            break
+        if event == 'Go':
+            # change the "output" element to be the value of "input" element
+            window['-OUT-'].update(values['-IN-'])
+        elif event.startswith('Dark'):
+            sg.theme('Dark Gray 13')
+            window.close()              # close the window
+            window = make_window()      # make a new window with the "same layout"
+
+    window.close()
+
+
+if __name__ == '__main__':
+    main()