Merge pull request #2629 from PySimpleGUI/Dev-latest

New multithreaded demo

DemoPrograms/Demo_Multithreaded_Animated_Shell_Command.py

@@ -0,0 +1,36 @@
+import subprocess
+import PySimpleGUI as sg
+import threading
+
+"""
+    Demo - Run a shell command while displaying an animated GIF to inform the user the 
+    program is still running.
+    If you have a GUI and you start a subprocess to run a shell command, the GUI essentually
+    locks up and often the operation system will off to terminate the program for you.
+
+    This demo fixes this situation by running the subprocess as a Thread.   This enables
+    the subproces to run async to the main program.  The main program then simply runs a loop,
+    waiting for the thread to complete running. 
+
+    The output from the subprocess is saved and displayed in a scrolled popup.
+"""
+
+
+def process_thread():
+    global proc
+    proc = subprocess.run('pip list', shell=True, stdout=subprocess.PIPE)
+
+
+thread = threading.Thread(target=process_thread, daemon=True)
+thread.start()
+
+while True:
+    sg.popup_animated(sg.DEFAULT_BASE64_LOADING_GIF, 'Loading list of packages', time_between_frames=100)
+    thread.join(timeout=.1)
+    if not thread.is_alive():
+        break
+sg.popup_animated(None)
+
+output = proc.__str__().replace('\\r\\n', '\n')
+sg.popup_scrolled(output)
+