New Demo Program - shows using objects instead of strings with Listbox

DemoPrograms/Demo_Listbox_Using_Objects.py

@@ -0,0 +1,43 @@
+import PySimpleGUI as sg
+
+"""
+    Demo - Listbox Using Objects
+
+    Several elements can take not just strings, but objects.  The Listsbox is one of them.
+    This demo show how you can use objects directly in a Listbox in a way that you can access
+        information about each object that is different than what is shown in the Window.
+
+    The important part of this design pattern is the use of the __str__ method in your item objects.
+        This method is what determines what is shown in the window.
+
+    Copyright 2022 PySimpleGUI
+"""
+
+class Item():
+    def __init__(self, internal, shown):
+        self.internal = internal
+        self.shown = shown
+
+    def __str__(self):
+        return self.shown
+
+# make list of some objects
+my_item_list = [Item(f'Internal {i}', f'shown {i}') for i in range(100)]
+
+layout = [  [sg.Text('Select 1 or more items and click "Go"')],
+            [sg.Listbox(my_item_list, key='-LB-', s=(20,20), select_mode=sg.LISTBOX_SELECT_MODE_EXTENDED)],
+            [sg.Output(s=(40,10))],
+            [sg.Button('Go'), sg.Button('Exit')]  ]
+
+window = sg.Window('Listbox Using Objects', layout)
+
+while True:
+    event, values = window.read()
+    # print(event, values)
+    if event == sg.WIN_CLOSED or event == 'Exit':
+        break
+    elif event == 'Go':
+        print('You selected:')
+        for item in values['-LB-']:
+            print(item.internal)
+window.close()