多处理映射函数与python中的列表

Question

我想映射一个带有字符串列表（url）的函数，以便并行执行。我的函数将url作为输入，并返回dictionary。请看一下我的代码：

from multiprocessing import Pool

def search_for(url):
        dicos = {}
        try:
            if always_true(url) == "True":
                  dicos['link'].append(url)
        except:
                  pass
        return dicos

def main():
  proc    = int( sys.argv[1]  )
  start_time = time.time()
  result_joomla = {'link': []}
  p = Pool(proc) 
  f = open("file.txt")
  lines = f.readlines()
  all = p.map(search_for, lines)
  for p in all:
        result["link"].append(p.get("link"))
  print( " Number of urls : " + str( len( result["link"] ) ) )
  print " links \n"
  for item in result["link"]:
        print item

if __name__ == '__main__':
      main()

此代码的执行永不停止，不显示任何内容 任何形式的帮助将不胜感激