python多进程中的内存复制(实例讲解)

def parse_lines(args):
 #working
 ...
def main_logic():
 f = open(filename , 'r')
 lines = f.readlines()
 f.close()
 pool = multiprocessing.Pool(processes==4)
 rel = pool.map(parse_lines , itertools.izip(lines , itertools.repeat(second_args)) , int(len(lines)/4))
 pool.close()
 pool.join()

def line_count(file_name):
 count = -1 #让空文件的行号显示0
 for count,line in enumerate(open(file_name)): pass
 #enumerate格式化成了元组,count就是行号,因为从0开始要+1
 return count+1
def parse_lines(args):
 f = open(args[0] , 'r')
 lines = f.readlines()[args[1]:args[2]] #read some lines
 f.close() 
 #working
def main_logic(filename,process_num):
 line_count = line_count(filename)
 avg_len = int(line_count/process_num)
 left_cnt = line_count%process_num;
 pool = multiprocessing.Pool(processes=process_num)
 for i in xrange(0,process_num):
  ext_cnt = (i>=process_num-1 and [left_cnt] or [0])[0]
  st_line = i*avg_len
  pool.apply_async(parse_lines, ((filename, st_line, st_line+avg_len+ext_cnt),)) #指定进程读某几行数据
 pool.close()
 pool.join()