Please guide me in the right direction if this is already answered. I have a GUI script that has several buttons and when I click the start button, it needs to send a message to a process which is using multiprocessing.Process(). This process is started in the main function. I am using a Queue object to send messages to this process. As an example, the process is an infinite while loop that terminates when it receives a ‘True’ value and ‘runs’ constantly for every ‘False’ value that it gets from the queue. There are two buttons, ‘start’ and ‘stop’. The ‘start’ button is what initiates this while loop that constantly sends ‘False’ to keep the process running. The ‘stop’ button sends a ‘True’ value that terminates the while loop, ending the process and eventually the program comes to an end. I read a few posts on something similar where people have recommended using asyncio to run the GUI and the process concurrently. The following is the class that creates the GUI:
import os
import threading
import tkinter as tk
from tkinter import *
from tkinter import filedialog, ttk
from tkinter.constants import DISABLED, NORMAL
from PIL import ImageTk, Image
import glob
import time
import multiprocessing
from multiprocessing import Queue, Process, Manager
import asyncio
import numpy as np
import queue
class App(tk.Tk):
"""
This class creates the GUI with the desired buttons and operations.
asyncio is used to run the GUI and the processes concurrently.
"""
def __init__(self):
global detection_queue, hit
super().__init__()
# self.attributes('-fullscreen', True)
# global detection_queue
self.geometry("750x600")
self.title('My_GUI')
self.setup_frame()
self.operate_frame()
self.main_frame()
self.detection_queue = detection_queue # Manager().Queue()
self.user_pressed_enter = False
self.hit = hit #Manager().Queue()
self.start = True
def setup_frame(self):
"""
Creates the first frame with functionalities to create a directory or browse folder where the
data needs to be stored.
"""
setup = tk.Frame(self, bg='grey')
setup.pack(padx=2, pady=2, ipadx=2, ipady=2, side=TOP)
self.b1 = Button(setup, text="Create destination directory", command=self.enter_dir)
self.b1.pack(padx=15, pady=15, ipadx=15, ipady=15, side='left')
browse_button = Button(setup, text='Browse Folder', command=self.browse_folder)
browse_button.pack(padx=15, pady=15, ipadx=15, ipady=15, side='left')
def operate_frame(self):
"""
This frame creates buttons that control the entire operation and execution of the processes.
"""
operate = tk.Frame(self, bg='grey')
operate.pack(side=BOTTOM)
# The start button runs the start_example method on a separate thread. Use .start instead of .start()
# b2 = Button(operate, text="Start", command=Thread(target=self.start_example).start, state='normal')
# running the following line on a separate thread did not work.
b2 = Button(operate, text="Start", command=lambda: [self.start_async_task, self.hit.put(False)],
state='normal') # lambda: [self.example(self.hit)]
b2.pack(padx=15, pady=15, ipadx=15, ipady=15, side='left')
b3 = Button(operate, text="Stop", command=lambda: [self.hit.put(True)],
state='normal') # lambda: [self.example(self.hit=True)]
b3.pack(padx=15, pady=15, ipadx=15, ipady=15, side='left')
b4 = Button(operate, text='Save', command=self.save_files, state='normal')
b4.pack(padx=15, pady=15, ipadx=15, ipady=15, side='left')
b5 = Button(operate, text='Close', command=self.close_app, state='normal')
b5.pack(padx=15, pady=15, ipadx=15, ipady=15, side='left')
open_button = tk.Button(self, text="Display Images", command=self.display_images, state='normal')
open_button.pack(padx=20, pady=10)
def start_async_task(self):
print('This is in "start_async_task"')
threading.Thread(target=self.run_async_task).start()
def run_async_task(self):
print('this is in "run_async_task"')
async def task():
"""
All this task is doing is passing booleans through the detection queue.
This task controls the processes created.
"""
global user_pressed_enter
print(f'This is user pressed enter: {user_pressed_enter}')
_hit = self.hit.get()
print(f'got hit as: {_hit}')
while not user_pressed_enter:
print('in the while loop of task function')
self.detection_queue.put(False)
print('detection queue sent False')
if _hit:
user_pressed_enter = True
self.detection_queue.put(True)
print('detection queue sent True')
# async def inner_task():
# await task()
asyncio.run(task())
print('ran the inner_task()...')
# loop = asyncio.new_event_loop()
# asyncio.set_event_loop(loop)
# asyncio.run_coroutine_threadsafe(inner_task(), loop)
def close_app(self):
self.destroy()
if __name__ == "__main__":
detection_queue = Manager().Queue()
hit = Manager().Queue()
print('created queues...')
user_pressed_enter = False
app = App()
my_p= Process(target=my_process, args=(detection_queue,))
my_p.start()
print('started the process...')
app.mainloop()
I have removed some methods as it does not pertain to the problem. The problem I face is that when the GUI launches and I click the ‘start’ button, there is NO response in the terminal. The close button works in ‘destroying’ the GUI window. When the start button is pushed, the following function should run and print random numbers:
def my_process(detection_queue):
shutdown_loop = False
while not shutdown_loop:
exit_queue_read = False
while not exit_queue_read:
print('Inside the inner while loop...')
try:
shutdown_loop_flag = detection_queue.get()
print(f"read from queue: {shutdown_loop_flag}")
if shutdown_loop_flag:
shutdown_loop = True
# break
except queue.Empty:
print('went into exception')
exit_queue_read = True
finally:
if queue.Empty and shutdown_loop:
print('went into finally block')
exit_queue_read = True
# Simulate something
a = np.random.randint(0, 100)
print(f'Number: {a}')
time.sleep(0.05)
print('process exit()')
to check exactly what’s happening, I included a print statement inside the inner while loop of ‘my_process’ and this is executed only once. It could be that the terminal freezes right after this print statement when it reaches ‘detection_queue.get()’.
Here’s what I tried and what I want this code to do. I know that the GUI runs on the main thread and the process is started on another. When I did not use asyncio, the GUI would hang as soon as I hit the ‘start’ button. But now, my problem seems to be sending messages using the queue system. There is something fundamental about multiprocessing/threading and the queue system that I am failing to understand as I am a beginner in this. Overall, I want the GUI to control the process depending on which button I press. This is the final traceback which is because of shutting down the process forcefully. My concern is not with the output but rather the operation of the GUI. I look forward to your suggestions.
created queues...
started the process...
Inside the inner while loop...
Process Process-4:
Traceback (most recent call last):
File "C:UsersRAOKAppDataLocalanaconda3Libmultiprocessingconnection.py", line 328, in _recv_bytes
nread, err = ov.GetOverlappedResult(True)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
BrokenPipeError: [WinError 109] The pipe has been ended
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "C:UsersRAOKAppDataLocalanaconda3Libmultiprocessingprocess.py", line 314, in _bootstrap
self.run()
File "C:UsersRAOKAppDataLocalanaconda3Libmultiprocessingprocess.py", line 108, in run
self._target(*self._args, **self._kwargs)
File "C:My_GUI_v3.py", line 290, in my_process
shutdown_loop_flag = detection_queue.get()
^^^^^^^^^^^^^^^^^^^^^
File "<string>", line 2, in get
File "C:UsersRAOKAppDataLocalanaconda3Libmultiprocessingmanagers.py", line 822, in _callmethod
kind, result = conn.recv()
^^^^^^^^^^^
File "C:UsersRAOKAppDataLocalanaconda3Libmultiprocessingconnection.py", line 250, in recv
buf = self._recv_bytes()
^^^^^^^^^^^^^^^^^^
File "C:UsersRAOKAppDataLocalanaconda3Libmultiprocessingconnection.py", line 337, in _recv_bytes
raise EOFError
EOFError
Thank you for your time on this! I highly appreciate it.
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