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Python中運(yùn)行并行任務(wù)技巧

 更新時(shí)間:2015年02月26日 09:15:25   投稿:junjie  
這篇文章主要介紹了Python中運(yùn)行并行任務(wù)技巧,本文給出了兩個(gè)示例,并用map來處理并行任務(wù),需要的朋友可以參考下

示例

標(biāo)準(zhǔn)線程多進(jìn)程,生產(chǎn)者/消費(fèi)者示例:
Worker越多,問題越大

復(fù)制代碼 代碼如下:

# -*- coding: utf8 -*-

import os
import time
import Queue
import threading
from PIL import Image

def create_thumbnail(filename, size=(128, 128)):
    try:
        fp, fmt = filename.rsplit('.', 1)
        im = Image.open(filename)
        im.thumbnail(size, Image.ANTIALIAS)
        im.save((fp + '_'+'x'.join(str(i) for i in size) + '.'+fmt), im.format)
        return '%s thumbnail success!' % filename
    except Exception:
        return '%s thumbnail failed!' % filename


def get_image_paths(folder):
    return [os.path.join(folder, f) for f in os.listdir(folder) if 'png' in f]


class Consumer(threading.Thread):
    def __init__(self, queue):
        threading.Thread.__init__(self)
        self._queue = queue

    def run(self):
        while True:
            content = self._queue.get()
            if isinstance(content, str) and content == 'quit':
                break
            respone = create_thumbnail(content)
        print 'Bye bye!'


def Producer():
    filenames = get_image_paths('images')
    queue = Queue.Queue()
    worker_threads = build_worker_pool(queue, 4)
    start_time = time.time()

    for filename in filenames:
        queue.put(filename)
    for worker in worker_threads:
        queue.put('quit')
    for worker in worker_threads:
        worker.join()

    print time.time() - start_time


def build_worker_pool(queue, size):
    workers = []
    for _ in range(size):
        worker = Consumer(queue)
        worker.start()
        workers.append(worker)
    return workers


if __name__ == '__main__':
    Producer()

map

Map能夠處理集合按順序遍歷,最終將調(diào)用產(chǎn)生的結(jié)果保存在一個(gè)簡單的集合當(dāng)中。

復(fù)制代碼 代碼如下:

# -*- coding: utf8 -*-

import os
import time
from multiprocessing import Pool
from PIL import Image

def create_thumbnail(filename, size=(128, 128)):
    try:
        fp, fmt = filename.rsplit('.', 1)
        im = Image.open(filename)
        im.thumbnail(size, Image.ANTIALIAS)
        im.save((fp + '_'+'x'.join(str(i) for i in size) + '.'+fmt), im.format)
        return '%s thumbnail success!' % filename
    except Exception:
        return '%s thumbnail failed!' % filename


def get_image_paths(folder):
    return [os.path.join(folder, f) for f in os.listdir(folder) if 'png' in f]


def main():
    filenames = get_image_paths('images')
    start_time = time.time()
   
    pool = Pool(4)
    pool.map(create_thumbnail, filenames)
    pool.close()
    pool.join()

    print time.time() - start_time


if __name__ == '__main__':
    main()

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