在 Python 中为列表中的每个项目线程化 [英] Threading in Python for each item in list

问题描述

我有一个列表 H = [item1, item2, item3....so on] 和一个函数，

def start(item1):p1 = 对 item1 做点什么返回 p1

我希望函数 start 应该为列表 H 中的每个项目并行运行.我知道多处理，但我已经有 4 个使用多处理并行运行的列表.而如何实现列表中每个项目的线程化?有人可以用示例代码解释一下吗.

谢谢！

解决方案

制作一个在线程中运行给定函数并存储结果的函数:

导入线程def run_item(f, item):result_info = [threading.Event(), None]定义运行():result_info[1] = f(item)result_info[0].set()threading.Thread(target=runit).start()返回 result_info

然后是另一个收集结果的函数:

def gather_results(result_infos):结果 = []对于 xrange(len(result_infos)) 中的 i:result_infos[i][0].wait()结果.追加(result_infos[i][1])返回结果

然后从主线程说 proc 是处理项目的函数，items 是要处理的项目列表:

#开始处理物品result_infos = [run_item(proc, item) for item in items]#收集结果(阻塞)结果=gather_results(result_infos)

示例用法:

<预><代码>>>>导入时间>>>def proc(项目):... time.sleep(2.0)...返回项目 * 2...>>>打印gather_results([run_item(proc, item) for item in [1, 2, 10, 100]])#2 秒后...[2, 4, 20, 200]

I have a list H = [item1, item2, item3....so on] and a function,

def start(item1):
    p1 = Do something to item1     
    return p1

I want the function start should run in parallel for each item in list H. I know multiprocessing, but I already have 4 list that runs in parallel using multiprocessing. While how the threading for each item in a list could be achieved? Can somebody please explain this with example code.

Thanks!

解决方案

Make a function which runs a given function in a thread and stores the result:

import threading
def run_item(f, item):
    result_info = [threading.Event(), None]
    def runit():
        result_info[1] = f(item)
        result_info[0].set()
    threading.Thread(target=runit).start()
    return result_info

Then another function to gather the results:

def gather_results(result_infos):
    results = [] 
    for i in xrange(len(result_infos)):
        result_infos[i][0].wait()
        results.append(result_infos[i][1])
    return results

Then from the main thread, say proc is the function that processes an item and items is your list of items to process:

#start processing the items
result_infos = [run_item(proc, item) for item in items]
#gather the results (blocking)
results = gather_results(result_infos)

Example usage:

>>> import time
>>> def proc(item):
...     time.sleep(2.0)
...     return item * 2
... 
>>> print gather_results([run_item(proc, item) for item in [1, 2, 10, 100]])
#2 seconds later...
[2, 4, 20, 200]

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