Python3 multiprocessing shared dictionary consume by all process - python-3.x

Question

I'm beginner for multiprocessing,
i would like to use multiprocessing for parallel code running with streaming data.
To start good, I have coded below and got error.
Could you please tell me correct way to print on the screen.
Code:
import sys
from multiprocessing import Process, Manager
import time
def producer(dic, name):
for i in range(10000):
dic["A"] = i
time.sleep(2)
def consumer(dic, name):
for i in range(10000):
aval = dic.get("A")
#print(f" {name} - Val = {aval}")
sys.stdout.write(f" {name} - Val = {aval}")
sys.stdout.flush()
time.sleep(2.2)
if __name__ == '__main__':
manager = Manager()
dic = manager.dict()
Process(target=producer, args=(dic,"TT")).start()
time.sleep(1)
Process(target=consumer, args=(dic,"Con1")).start()
Process(target=consumer, args=(dic,"Con2")).start()
When I run the same in the windows console, I got below error, how can I print Consumer's print function in the console.Thanks
(base) PS D:\> python .\mulpro.py
Process Process-3:
Process Process-4:
Traceback (most recent call last):
File "C:\ProgramData\Anaconda3\lib\multiprocessing\managers.py", line 811, in
_callmethod
conn = self._tls.connection
AttributeError: 'ForkAwareLocal' object has no attribute 'connection'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "C:\ProgramData\Anaconda3\lib\multiprocessing\process.py", line 297, in _
bootstrap
self.run()
File "C:\ProgramData\Anaconda3\lib\multiprocessing\process.py", line 99, in ru
n
self._target(*self._args, **self._kwargs)
File "D:\mulpro.py", line 19, in consumer
aval = dic.get("A")
File "<string>", line 2, in get
File "C:\ProgramData\Anaconda3\lib\multiprocessing\managers.py", line 815, in
_callmethod
self._connect()
File "C:\ProgramData\Anaconda3\lib\multiprocessing\managers.py", line 802, in
_connect
conn = self._Client(self._token.address, authkey=self._authkey)
File "C:\ProgramData\Anaconda3\lib\multiprocessing\connection.py", line 490, i
n Client
c = PipeClient(address)
Traceback (most recent call last):
File "C:\ProgramData\Anaconda3\lib\multiprocessing\connection.py", line 691, i
n PipeClient
_winapi.WaitNamedPipe(address, 1000)
File "C:\ProgramData\Anaconda3\lib\multiprocessing\managers.py", line 811, in
_callmethod
conn = self._tls.connection
FileNotFoundError: [WinError 2] The system cannot find the file specified
AttributeError: 'ForkAwareLocal' object has no attribute 'connection'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "C:\ProgramData\Anaconda3\lib\multiprocessing\process.py", line 297, in _
bootstrap
self.run()
File "C:\ProgramData\Anaconda3\lib\multiprocessing\process.py", line 99, in ru
n
self._target(*self._args, **self._kwargs)
File "D:\mulpro.py", line 19, in consumer
aval = dic.get("A")
File "<string>", line 2, in get
File "C:\ProgramData\Anaconda3\lib\multiprocessing\managers.py", line 815, in
_callmethod
self._connect()
File "C:\ProgramData\Anaconda3\lib\multiprocessing\managers.py", line 802, in
_connect
conn = self._Client(self._token.address, authkey=self._authkey)
File "C:\ProgramData\Anaconda3\lib\multiprocessing\connection.py", line 490, i
n Client
c = PipeClient(address)
File "C:\ProgramData\Anaconda3\lib\multiprocessing\connection.py", line 691, i
n PipeClient
_winapi.WaitNamedPipe(address, 1000)
FileNotFoundError: [WinError 2] The system cannot find the file specified
Process Process-2:
Traceback (most recent call last):
File "C:\ProgramData\Anaconda3\lib\multiprocessing\process.py", line 297, in _
bootstrap
self.run()
File "C:\ProgramData\Anaconda3\lib\multiprocessing\process.py", line 99, in ru
n
self._target(*self._args, **self._kwargs)
File "D:\mulpro.py", line 13, in producer
dic["A"] = i
File "<string>", line 2, in __setitem__
File "C:\ProgramData\Anaconda3\lib\multiprocessing\managers.py", line 818, in
_callmethod
conn.send((self._id, methodname, args, kwds))
File "C:\ProgramData\Anaconda3\lib\multiprocessing\connection.py", line 206, i
n send
self._send_bytes(_ForkingPickler.dumps(obj))
File "C:\ProgramData\Anaconda3\lib\multiprocessing\connection.py", line 280, i
n _send_bytes
ov, err = _winapi.WriteFile(self._handle, buf, overlapped=True)
BrokenPipeError: [WinError 232] The pipe is being closed

Answer 1

The reason might be that the main process doesn't wait for two children process, so make your code like this could work:
def run():
manager = Manager()
dic = manager.dict()
Process(target=producer, args=(dic,"TT")).start()
time.sleep(1)
Process(target=consumer, args=(dic,"Con1")).start()
Process(target=consumer, args=(dic,"Con2")).start()
while True:
pass
if __name__ == '__main__':
run()
However it's very strange that if I append a dead loop in main instead of using another function, it still raise that exception. Anyway, the code above could help.