In order to create queues in Python, we have to import the Queue class from the queue module. Add the following statement towards the top of our GUI module:

    from threading import Thread 
    from queue import Queue

That gets us started.

Next, we create a queue instance:

    def use_queues(self): 
        gui_queue = Queue()                    # create queue instance 
        print(gui_queue)                       # print instance

We call the method within our button click event:

    # Button callback
    def click_me(self): 
        self.action.configure(text='Hello ' + self.name.get())
        self.create_thread()
        self.use_queues()

Now we have an instance of a queue. We can prove that this works by printing it out:

In order to put the data into the queue, we use the put command. In order to get the data out of the queue, we use the get command:

    # Create Queue instance   
    def use_queues(self):
       gui_queue = Queue() 
       print(gui_queue)
       gui_queue.put('Message from a queue') 
       print(gui_queue.get())

Running the modified code results in the message first being placed in the Queue, then being taken out of the Queue, and then being printed to the console:

We can place many messages into the Queue:

    # Create Queue instance 
    def use_queues(self):
        gui_queue = Queue() 
        print(gui_queue)
        for idx in range(10):
            gui_queue.put('Message from a queue: ' + str(idx))
        print(gui_queue.get())

We have placed ten messages into Queue, but we are only getting the first one out. The other messages are still inside Queue, waiting to be taken out in a FIFO fashion:

In order to get all the messages that have been placed into Queue out, we can create an endless loop:

GUI_queues_put_get_loop_endless.py

    # Create Queue instance 
    def use_queues(self):
        gui_queue = Queue() 
        print(gui_queue)
        for idx in range(10):
            gui_queue.put('Message from a queue: ' + str(idx))
        while True: 
            print(gui_queue.get())

Running the preceding code results in the following screenshot:

While this code works, unfortunately, it freezes our GUI. In order to fix this, we have to call the method in its own thread, as we did in the previous recipes.

Let's run our Queue method in a thread:

    # Running methods in Threads 
    def create_thread(self):
        self.run_thread = Thread(target=self.method_in_a_thread, args=
                                 [8]) 
        self.run_thread.setDaemon(True) 
        self.run_thread.start()

        # start queue in its own thread
        write_thread = Thread(target=self.use_queues, daemon=True)
        write_thread.start()

    # Button callback
    def click_me(self): 
        self.action.configure(text='Hello ' + self.name.get())
        self.create_thread()
        # now started as a thread in create_thread()
        # self.use_queues()

When we now click the action button, the GUI no longer freezes and the code works:

GUI_queues_put_get_loop_endless_threaded.py