python多进程处理数据

#coding=utf-8
from multiprocessing import Process

def target_function(index,sublist):
    print index,sublist


if __name__=="__main__":
    TXT_FILE = "path/to/imagelist.txt"
    n_processes = 50 #number of processes
    f = open(TXT_FILE,‘r‘)
    image_list = f.readlines()
    f.close()
    n_total = len(image_list)
    length = float(n_total) / float(n_processes)
    indices = [int(round(i* length)) for i in range(n_processes)]

    sublists = [image_list[indices[i]:indices[i+1]] for i in range(n_processes)]
    processes = [Process(target=target_function,args=(i,x)) for i,x in enumerate(sublists)]

    for p in processes:
        p.start()
    for p in processes:
        p.join()