[Python] tkinter - generate_event not working when called from a background thread

I'm trying to update some UI elements from a background thread, since tkinter doesn't support that I tried to create a queue for generating events with event_generate.

So every time I need some kind of update I have to insert a ticket into this queue:

from enum import Enum, auto
from queue import Queue
from ttkbootstrap import Window



class TicketPurpose(Enum):
UPDATE_LOG_TEXT = auto()


class Ticket:
def __init__(self, ticket_type : TicketPurpose, ticket_value : str):
self.ticket_type = ticket_type
self.ticket_value = ticket_value




class QueueMaster():

__instance = None

@staticmethod
def get_instance():
"""singleton """

if QueueMaster.__instance is None:
raise Exception("No instance available yet!")
return QueueMaster.__instance

def __init__(self, root : Window):
if QueueMaster.__instance is not None:
raise Exception("Singleton cannot be instantiated more than once!")
else:
QueueMaster.__instance = self
self.queue = Queue()
self.root = root

def put_ticket(self, ticket : Ticket):
"""puts a ticket into the queue"""

print(f"inserting ticket: {ticket.ticket_value}")
self.queue.put(ticket)
#self.root.after(0, lambda : self.root.event_generate("<<CheckQueue>>"))
self.root.event_generate("<<CheckQueue>>")


def get_ticket(self):
"""gets a tickted from the queue"""

ticket = self.queue.get()
print(f"removed {ticket.ticket_value} from queue")
return ticket

def queue_empty(self):
"""check if queue is empty"""

return self.queue.empty()


my main file has a simple function called foo which is executed from a background thread and inserts a ticket into the queue:

class MainWindow():

def __init__(self, root):
self.root = root
self.ticket_queue = None
self.ticket_queue = QueueMaster(self.root)
self.__init_window()

def main_loop(self):
"""starts the main loop"""

self.root.mainloop()

def foo(self):
"""test function"""

self.ticket_queue.put_ticket(Ticket(ticket_type=TicketPurpose.UPDATE_LOG_TEXT, ticket_value="foo"))
sleep(2)

def check_queue(self, event=None):
"""update ui"""

ticket = self.ticket_queue.get_ticket()
if ticket.ticket_type == TicketPurpose.UPDATE_LOG_TEXT:
print("updating...")
else:
raise Exception("Invalid ticket!")


def __init_window(self):
"""init the window and widgets"""

self.root.bind("<<CheckQueue>>", self.check_queue)
thread = threading.Thread(target = self.foo, daemon = True)
thread.start()





def main():
"""main"""

root = ttkb.Window(themename = "litera")
root.title("test")
root.minsize(800, 600)

main_window = MainWindow(root)
main_window.main_loop()


if __name__ == "__main__":
main()


I'm also binding to a method called check_queue here so that every time an event is generated I'll have a chance to handle it, the problem is that this method isn't being called at all, what am I doing wrong?

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