New imports... switched order so that PyCharm will pick up with Python 3 import first

ProgrammingClassExamples/5a PSG (listboxes add remove).py

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+#PySimple examples (v 3.8)
+#Tony Crewe
+#Sep 2018
+
+import PySimpleGUI as sg
+
+sg.ChangeLookAndFeel('BlueMono')
+
+#use column feature with height listbox takes up
+column1 = [
+    [sg.Text('Add or Delete Items\nfrom a Listbox', font = ('Arial', 12, 'bold'))],
+     [sg.InputText( size = (15,1), key = 'add'), sg.ReadButton('Add')],
+    [sg.ReadButton('Delete selected entry')]]
+
+List = ['Austalia', 'Canada', 'Greece']         #initial listbox entries
+
+#add initial List  to listbox
+layout = [
+    [sg.Listbox(values=[l for l in List], size = (30,8), key ='listbox'),
+     sg.Column(column1)]]
+
+window = sg.Window('Listbox').Layout(layout)
+
+while True:
+    button, value = window.Read()
+    if button is not None:
+                                                    #value[listbox] returns a list
+        if button == 'Delete selected entry':       #using value[listbox][0] give the string
+            if value['listbox'] == []:               #ensure something is selected
+                sg.Popup('Error','You must select a Country')
+            else:
+                List.remove(value['listbox'][0])    #find and remove this
+        if button == 'Add':
+            List.append(value['add'])           #add string in add box to list
+        List.sort()                             #sort
+        #update listbox
+        window.FindElement('listbox').Update(List)
+    else:
+        break