Merge pull request PySimpleGUI#1406 from PySimpleGUI/Dev-latest

MikeTheWatchGuy · web-flow · commit 6af5d9176b0b · 2019-05-14T14:24:00.000-04:00
New Demo program showing long tasks
diff --git a/DemoPrograms/Demo_Threaded_Work.py b/DemoPrograms/Demo_Threaded_Work.py
@@ -0,0 +1,74 @@
+#!/usr/bin/python3
+import queue
+import threading
+import time
+
+import PySimpleGUI as sg
+
+# Put your long-running code in here
+def worker_thread(thread_name, gui_queue):
+    print('Starting thread - {} '.format(thread_name))
+    # this is our "long running function call"
+    time.sleep(5)  # sleep for a while
+
+    # at the end of the work, before exiting, send a message back to the GUI indicating end
+    gui_queue.put('{} - done'.format(thread_name))  # put a message into queue for GUI
+
+
+######   ##     ## ####
+##    ##  ##     ##  ##
+##        ##     ##  ##
+##   #### ##     ##  ##
+##    ##  ##     ##  ##
+##    ##  ##     ##  ##
+######    #######  ####
+
+def the_gui(gui_queue):
+
+    layout = [[sg.Text('Multithreaded Work Example')],
+              [sg.Text('', size=(25, 1), key='_OUTPUT_')],
+              # [sg.Output(size=(40,6))],
+              [sg.Button('Go'), sg.Button('Exit')], ]
+
+    window = sg.Window('Multithreaded Window').Layout(layout)
+    # --------------------- EVENT LOOP ---------------------
+    message = None
+    while True:
+        event, values = window.Read(timeout=100)  # wait for up to 100 ms for a GUI event
+        if event is None or event == 'Exit':
+            break
+        if event == 'Go':
+            window.Element('_OUTPUT_').Update('Starting long work....')
+            # simulate STARTING long run by starting a thread
+            threading.Thread(target=worker_thread, args=('Thread 1', gui_queue,), daemon=True).start()
+
+        # --------------- Loop through all messages coming in from threads ---------------
+        try:  # see if something has been posted to Queue
+            message = gui_queue.get_nowait()
+        except queue.Empty:  # get_nowait() will get exception when Queue is empty
+            pass             # nothing in queue so do nothing
+
+        # if message received from queue, display the message in the Window
+        if message is not None and message.startswith('Thread 1'):
+            # this is the place you would execute code at ENDING of long running task
+            window.Element('_OUTPUT_').Update(message)
+            window.Refresh()  # do a refresh because could be showing multiple messages before next Read
+            message = None
+
+    # if user exits the window, then close the window and exit the GUI func
+    window.Close()
+
+
+##     ##    ###    #### ##    ##
+###   ###   ## ##    ##  ###   ##
+#### ####  ##   ##   ##  ####  ##
+## ### ## ##     ##  ##  ## ## ##
+##     ## #########  ##  ##  ####
+##     ## ##     ##  ##  ##   ###
+##     ## ##     ## #### ##    ##
+
+if __name__ == '__main__':
+    # -- Create a Queue to communicate with GUI --
+    gui_queue = queue.Queue()  # queue used to communicate between the gui and the threads
+    the_gui(gui_queue)
+    print('Exiting Program')
