如何在连续循环中使用python多处理池

Question

我正在使用 python 多处理库来执行 selenium 脚本。我的代码如下：

#-- start and join multiple threads ---
thread_list = []
total_threads=10 #-- no of parallel threads
for i in range(total_threads):
    t = Process(target=get_browser_and_start, args=[url,nlp,pixel])
    thread_list.append(t)
    print "starting thread..."
    t.start()

for t in thread_list:
    print "joining existing thread..."
    t.join()

据我了解join() 函数，它将等待每个进程完成。但是我希望一旦一个进程被释放，它就会被分配另一个任务来执行新的功能。

可以这样理解：

假设首先启动了 8 个进程。

no_of_tasks_to_perform = 100

for i in range(no_of_tasks_to_perform):
    processes start(8)
    if process no 2 finished executing, start new process
    maintain 8 process at any point of time till 
    "i" is <= no_of_tasks_to_perform

Answer 1

不要时不时启动新进程，而是尝试将所有任务放入multiprocessing.Queue()，并启动8个长时间运行的进程，在每个进程中不断访问任务队列以获得新的任务，然后做这项工作，直到没有任务了。

在你的情况下，它更像是这样的：

from multiprocessing import Queue, Process

def worker(queue):
    while not queue.empty():
        task = queue.get()

        # now start to work on your task
        get_browser_and_start(url,nlp,pixel) # url, nlp, pixel can be unpacked from task

def main():
    queue = Queue()

    # Now put tasks into queue
    no_of_tasks_to_perform = 100

    for i in range(no_of_tasks_to_perform):
        queue.put([url, nlp, pixel, ...]) 

    # Now start all processes
    process = Process(target=worker, args=(queue, ))
    process.start()
    ...
    process.join()