【python 进程】进程池加锁

当使用多进程对同一个文件进行操作时,为了避免冲突的发生,需要使用进程锁来对程序进行阻塞,以保证程序的正常运行。

多进程加锁:

from multiprocessing import Pool,Process

def demo01(pid,lock):
	lock.acquire()
	with open('file.txt',"a+", encoding='utf-8') as f:
		f.write(pid)
		...
	...
	lock.release()

lock = Lock()
for i in range(3):
	i = str(i)
	pool = Process(target=demo01,args=(i,lock))
	pool.start()

进程池加锁

错误加锁

lock = Lock()
pid = [(str(i), lock) for i in range(5)]
pool = Pool(5)
pool.map(demo01, pid)
pool.close()
pool.join()

像单进程这种将锁对象以参数传入的方法,如果直接应用于多进程中,会抛出一个异常
RuntimeError: Lock objects should only be shared between processes through inheritance

解决方案一:
在创建进程池对象时,传递Lock,将其变成一个对于面向所有子进程的全局对象

def demo01(pid, lock):
    lock.acquire()
    with open('file.txt', "a+", encoding='utf-8') as f:
        print(pid)
        f.write(str(pid))
        ...
    ...
    lock.release()


def init(l):
    global lock
    lock = l


if __name__ == '__main__':
    lock = Lock()
    pid = [(str(i), lock) for i in range(5)]
    pool = Pool(5,initializer=init,initargs=(lock,))
    pool.map(demo01, pid)
    pool.close()
    pool.join()

解决方案二:
使用Manager()。

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