I am having the following issue:
I am trying to use concurrent.futures.ProcessPoolExecutor(), or anything similar, and show the progress of each process on a tkinter widget.
There is this answer: Python Tkinter multiprocessing progress but I can not quite make it to work.
The following simplified version of my code seems to work only when using ThreadPoolExecutor() which I do not want.
Thanks in advance for any help!
import concurrent.futures
import tkinter
import tkinter.ttk
import multiprocessing
import random
import time
class App:
def __init__(self, root):
self.root = root
self.processes = 5
self.percentage = []
self.changing_labels = []
self.queues = []
self.values = []
for i in range(self.processes):
temp_percentage = tkinter.StringVar()
temp_percentage.set("0 %")
self.percentage.append(temp_percentage)
temp_changing_label = tkinter.Label(self.root, textvariable=temp_percentage)
temp_changing_label.pack()
self.changing_labels.append(temp_changing_label)
self.queues.append(multiprocessing.Queue())
# Just same values that I want to do calculations on
temp_value = []
for ii in range(12):
temp_value.append(random.randrange(10))
self.values.append(temp_value.copy())
self.start_processing()
def start_processing(self):
def save_values(my_values): # Save my new calculated values on the same file or different file
with open(f"example.txt", "a") as file:
for v in my_values:
file.write(str(v))
file.write(" ")
file.write("\n")
def work(my_values, my_queue): # Here I do all my work
# Some values to calculate my progress so that I can update my Labels
my_progress = 0
step = 100 / len(my_values)
# Do some work on the values
updated_values = []
for v in my_values:
time.sleep(0.5)
updated_values.append(v 1)
my_progress = step
my_queue.put(my_progress) # Add current progress to queue
save_values(updated_values) # Save it before exiting
# This Part does no work with ProcessPoolExecutor, with ThreadPoolExecutor it works fine
with concurrent.futures.ProcessPoolExecutor() as executor:
results = [executor.submit(work, self.values[i], self.queues[i])
for i in range(self.processes)]
# Run in a loop and update Labels or exit when done
while True:
results_done = [result.done() for result in results]
if False in results_done:
for i in range(self.processes):
if results_done[i] is False:
if not self.queues[i].empty():
temp_queue = self.queues[i].get()
self.percentage[i].set(f"{temp_queue:.2f} %")
else:
self.percentage[i].set("100 %")
self.root.update()
else:
break
# Close window at the very end
self.root.destroy()
def main(): # Please do not change my main unless it is essential
root = tkinter.Tk()
my_app = App(root)
root.mainloop()
if __name__ == "__main__":
main()
CodePudding user response：
The problem is caused by an exception being thrown inside the new processes. To see this exception, you can call the Future.result function, which raises the exception, e.g.
print([result.result() for result in results])
This gives the error AttributeError: Can't pickle local object 'App.start_processing.<locals>.work', so the problem is that work was defined inside another function.
After moving the work and save_values functions out of the start_processing method, the error changes to RuntimeError: Queue objects should only be shared between processes through inheritance. This can be fixed by using a multiprocessing.Manager to create the queues:
class App:
def __init__(self, root):
...
with multiprocessing.Manager() as manager:
for i in range(self.processes):
...
self.queues.append(manager.Queue())
...
self.start_processing()
The print([result.result() for result in results]) debugging line can now be removed.
The full code is as follows:
import concurrent.futures
import tkinter
import tkinter.ttk
import multiprocessing
import random
import time
class App:
def __init__(self, root):
self.root = root
self.processes = 5
self.percentage = []
self.changing_labels = []
self.queues = []
self.values = []
with multiprocessing.Manager() as manager:
for i in range(self.processes):
temp_percentage = tkinter.StringVar()
temp_percentage.set("0 %")
self.percentage.append(temp_percentage)
temp_changing_label = tkinter.Label(self.root, textvariable=temp_percentage)
temp_changing_label.pack()
self.changing_labels.append(temp_changing_label)
self.queues.append(manager.Queue())
# Just same values that I want to do calculations on
temp_value = []
for ii in range(12):
temp_value.append(random.randrange(10))
self.values.append(temp_value.copy())
self.start_processing()
@staticmethod
def save_values(my_values): # Save my new calculated values on the same file or different file
with open(f"example.txt", "a") as file:
for v in my_values:
file.write(str(v))
file.write(" ")
file.write("\n")
@classmethod
def work(cls, my_values, my_queue): # Here I do all my work
# Some values to calculate my progress so that I can update my Labels
my_progress = 0
step = 100 / len(my_values)
# Do some work on the values
updated_values = []
for v in my_values:
time.sleep(0.5)
updated_values.append(v 1)
my_progress = step
my_queue.put(my_progress) # Add current progress to queue
cls.save_values(updated_values) # Save it before exiting
def start_processing(self):
# This Part does no work with ProcessPoolExecutor, with ThreadPoolExecutor it works fine
with concurrent.futures.ProcessPoolExecutor() as executor:
results = [executor.submit(self.work, self.values[i], self.queues[i])
for i in range(self.processes)]
# Run in a loop and update Labels or exit when done
while True:
results_done = [result.done() for result in results]
if False in results_done:
for i in range(self.processes):
if results_done[i] is False:
if not self.queues[i].empty():
temp_queue = self.queues[i].get()
self.percentage[i].set(f"{temp_queue:.2f} %")
else:
self.percentage[i].set("100 %")
self.root.update()
else:
break
# Close window at the very end
self.root.destroy()
def main(): # Please do not change my main unless it is essential
root = tkinter.Tk()
my_app = App(root)
root.mainloop()
if __name__ == "__main__":
main()
PS: I would recommend not all(results_done) rather than False in results_done, and not results_done[i] rather than results_done[i] is False.