How to start timer and reset it back in python?

Question

I have initialize a timer on class where after specified seconds, it will called another target function. The situation is on load, it will display welcome function gui and open the serial port.

On data received through serial port, I want to enquiry the information on my web api and after display the information, I want to start the timer that has been declared on __init__.

But if another data coming through the serial port before the timer hit, I want the timer to restart/reset as more data coming, I don't have to show welcome function again until there is nothing coming between the timer run.

I have found something from this answer, but it does not trigger callback function

from threading import Thread, Timer

class TimerThread(threading.Thread):
    def __init__(self, timeout=3, sleep_chunk=0.25, callback=None, *args):
        threading.Thread.__init__(self)
        print('timer:initialized')
        self.timeout = timeout
        print('timeout:' + str(timeout))
        self.sleep_chunk = sleep_chunk
        print('timeout:' + str(sleep_chunk))
        if callback == None:
            self.callback = None
            print('callback:none')
        else:
            self.callback = callback
            print('callback:' + str(callback))
        self.callback_args = args

        self.terminate_event = threading.Event()
        self.start_event = threading.Event()
        self.reset_event = threading.Event()
        self.count = self.timeout/self.sleep_chunk

    def run(self):
        print('timer:run')
        while not self.terminate_event.is_set():
            while self.count > 0 and self.start_event.is_set():
                if self.reset_event.wait(self.sleep_chunk):  # wait for a small chunk of timeout
                    self.reset_event.clear()
                    self.count = self.timeout/self.sleep_chunk  # reset
                self.count -= 1
            if self.count <= 0:
                self.start_event.clear()
                print('timeout. calling function...')
                self.callback(*self.callback_args)
                self.count = self.timeout/self.sleep_chunk  # reset

    def start_timer(self):
        print('start_timer')
        self.start_event.set()

    def stop_timer(self):
        print('stop_timer')
        self.start_event.clear()
        self.count = self.timeout / self.sleep_chunk  # reset

    def restart_timer(self):
        # reset only if timer is running. otherwise start timer afresh
        print('restart_timer')
        if self.start_event.is_set():
            self.reset_event.set()
            print('restart_timer:reset')
        else:
            self.start_event.set()
            print('restart_timer:start')

    def terminate(self):
        print('terminate')
        self.terminate_event.set()

class Application(Tk):
    def show_idle_screen(self):
        for widget in self.winfo_children():
            widget.destroy()
        # Create new widget element

    def show_product_info(self, barcodeno):
        # call web api and get response
        # create information widget element
        # -Timer(5.0, self.show_idle_screen).start()
        tmr = TimerThread(timeout, sleep_chunk, Application().show_idle_screen)
        tmr.restart_timer()


    def serial_port_data_received(self):
        if self.serial.inWaiting() > 0:
            # The rest of handling serial data
            # UPDATED CODE START
            # -if self.idle_timer.is_alive():
            #     -print('cancelling timer')
            #     -self.idle_timer.cancel()
            # UPDATED CODE END
            self.query_thread = Thread(target=lambda: self.show_product_info(barcodedata))
            self.query_thread.start()


    def __init__(self):
            # Initialization of timer
            # -self.idle_timer = Timer(5.0, self.show_idle_screen)
            self.new_thread = Thread(target=self.show_idle_screen)
            self.new_thread.start()

root = Application()
root.mainloop()

Log:

timer:initialized
timeout:6
timeout:0.25
callback:<bound method Application.show_idle_screen of <__main__.Application object .>>
start_timer

btw: `Thread(target=self.show_product_info, args=(barcodedata,))` — furas, Oct 08 '20 at 09:12
[Timer](https://docs.python.org/3/library/threading.html#timer-objects) has function `cancel()` to stop the timer. You will have to stop timer and create new `Timer` — furas, Oct 08 '20 at 09:15
Does this answer your question? [How to set a timer & clear a timer?](https://stackoverflow.com/questions/24968311/how-to-set-a-timer-clear-a-timer) — mkrieger1, Oct 08 '20 at 09:16
(the answer to your question is contained in the question, you already know the answer to the other question - sorry if this sounds confusing) — mkrieger1, Oct 08 '20 at 09:16
@furas, having `args` make an error `TypeError: show_product_info() takes 2 positional arguments but 14 were given`. — Luiey, Oct 08 '20 at 09:17
it is strange because you set only one value `args=(barcodedata,)`. OR maybe you used wrong code - `args=barcodedata` - `args` has to be tuple `(barcodedata,)` even if you have only one value. — furas, Oct 08 '20 at 09:19
@mkrieger1 I have follow earlier from the question. and when new data coming, I have check `if self.idle_timer.is_alive():` to cancel it first and put a print log to see if it coming in. But no, it is not detecting it already start on thread — Luiey, Oct 08 '20 at 09:20
in `__init__` you create `Timer` - `self.idle_timer = Timer(...)` but you forgot to start it `self.idle_timer.start()` — furas, Oct 08 '20 at 09:21
@furas the argument is followed from someone i saw on internet. i have run it and it show no error for the thread with arguments. — Luiey, Oct 08 '20 at 09:22
@furas i'm not sure what the error. but i got `AttributeError: 'NoneType' object has no attribute 'is_alive'` when i scan the barcode and check for `if self.idle_timer.is_alive():` — Luiey, Oct 08 '20 at 09:24

score 0 · Answer 1 · answered Oct 09 '20 at 09:10

I finally able to run what I desired after try and error.

from threading import Thread, Timer

class TimerThread(threading.Thread):
    def __init__(self, timeout=3, sleep_chunk=0.25, callback=None, *args):
        threading.Thread.__init__(self)
        print('timer:initialized')
        self.timeout = timeout
        print('timeout:' + str(timeout))
        self.sleep_chunk = sleep_chunk
        print('timeout:' + str(sleep_chunk))
        if callback == None:
            self.callback = None
            print('callback:none')
        else:
            self.callback = callback
            print('callback:' + str(callback))
        self.callback_args = args

        self.terminate_event = threading.Event()
        self.start_event = threading.Event()
        self.reset_event = threading.Event()
        self.count = self.timeout/self.sleep_chunk

    def run(self):
        print('timer:run')
        while not self.terminate_event.is_set():
            while self.count > 0 and self.start_event.is_set():
                if self.reset_event.wait(self.sleep_chunk):  # wait for a small chunk of timeout
                    self.reset_event.clear()
                    self.count = self.timeout/self.sleep_chunk  # reset
                self.count -= 1
            if self.count <= 0:
                self.start_event.clear()
                print('timeout. calling function...')
                self.callback(*self.callback_args)
                self.count = self.timeout/self.sleep_chunk  # reset

    def start_timer(self):
        print('start_timer')
        self.start_event.set()

    def stop_timer(self):
        print('stop_timer')
        self.start_event.clear()
        self.count = self.timeout / self.sleep_chunk  # reset

    def restart_timer(self):
        # reset only if timer is running. otherwise start timer afresh
        print('restart_timer')
        if self.start_event.is_set():
            self.reset_event.set()
            print('restart_timer:reset')
        else:
            self.start_event.set()
            print('restart_timer:start')

    def terminate(self):
        print('terminate')
        self.terminate_event.set()

class Application(Tk):
    def show_idle_screen(self):
        for widget in self.winfo_children():
            widget.destroy()
        # Create new widget element
        print('idle_screen')

    def show_product_info(self, barcodeno):
        # call web api and get response
        # create information widget element
        # -Timer(5.0, self.show_idle_screen).start()
        # -tmr = TimerThread(timeout, sleep_chunk, Application().show_idle_screen)
        # -tmr.restart_timer()
        self.tmr.restart_timer()


    def serial_port_data_received(self):
        if self.serial.inWaiting() > 0:
            # The rest of handling serial data
            # UPDATED CODE START
            # -if self.idle_timer.is_alive():
            #     -print('cancelling timer')
            #     -self.idle_timer.cancel()
            # UPDATED CODE END
            self.query_thread = Thread(target=lambda: self.show_product_info(barcodedata))
            self.query_thread.start()


    def __init__(self):
            # Initialization of timer
            # -self.idle_timer = Timer(5.0, self.show_idle_screen)
            self.tmr = TimerThread(timeout, sleep_chunk, self.show_idle_screen)
            self.tmr.start()
            self.tmr.start_timer()
            self.new_thread = Thread(target=self.show_idle_screen)
            self.new_thread.start()

root = Application()
root.mainloop()

Log:

idle_screen
timeout. calling function...
idle_screen
Going to query information for data
restart_timer
restart_timer:start
timeout. calling function...
idle_screen
Going to query information for data

How to start timer and reset it back in python?

1 Answers1