多处理错误：AssertionError：无法启动一个进程两次

Question

假设 function update_values 有一些 firebase 命令需要大约 2 秒才能执行，但我不想停止相机并等待。 所以我使用了多处理，这样相机就不会停止，代码仍然会更新值，但我正面临这个问题。 AssertionError: cannot start a process twice我应该如何解决这个问题？

import cv2
import numpy as np
from firebase import firebase
from firebase.firebase import FirebaseApplication
import multiprocessing

def update_values():
    x=np.random.randint(100)
    print("Updating Values") 
    print("done")

cap=cv2.VideoCapture(0)


#for improving fps
flag=0
#establishing connnection with the database for the first time
firebase_message = firebase.FirebaseApplication("<link to database>", None)    #reconnecting to the existing table
print("Connectionion Established")

t1 = multiprocessing.Process(target=update_values)

count_down=0
count_up=0
while(cap.isOpened()):
    _,frame=cap.read()
    x=np.random.randint(100)
    if(flag%100==0):
            t1.start()
    flag+=1
    cv2.imshow('frame',result)
    k = cv2.waitKey(1) & 0xff
    if k == ord('q'):
        break
cap.release()
cv2.destroyAllWindows()

Answer 1

哪个操作系统？ 在 Windows 上，多处理调用必须受if __name__=='__main__':保护，以防止无限进程创建

Python - 多处理错误“无法启动一个进程两次”

Answer 2

所以，我切换到线程，每次进入 if 条件时我都会创建新线程......这是代码......

import cv2
import numpy as np
from firebase import firebase
from firebase.firebase import FirebaseApplication
import threading

cap=cv2.VideoCapture(0)

#for improving fps
flag=0
#establishing connnection with the database for the first time
firebase_message = firebase.FirebaseApplication("<link to database>", None)    #reconnecting to the existing table
print("Connectionion Established")

def update_values():
    x=np.random.randint(100)
    print("Updating Values")
    print("done")



count_down=0
count_up=0
while(cap.isOpened()):
    _,frame=cap.read()
    
    x=np.random.randint(100)
    
    if(flag%100==0):
            t1 = threading.Thread(target=update_values)    
            t1.start()
            print("Done")
    flag+=1
    cv2.imshow('frame',result)
    k = cv2.waitKey(1) & 0xff
    if k == ord('q'):
        break
cap.release()
cv2.destroyAllWindows()