出现 TypeError：无法 pickle _thread.lock 对象

我正在查询 MongoDB 以获取字典列表，对于列表中的每个字典，我正在对值进行一些比较。根据比较结果，我将字典的值、比较结果和计算出的其他值存储在 mongoDB 集合中。我试图通过调用多处理来做到这一点，但收到此错误。

def save_for_doc(doc_id):

    #function to get the fields of doc
    fields = get_fields(doc_id)
    no_of_process = 5
    doc_col_size = 30000
    chunk_size = round(doc_col_size/no_of_process)
    chunk_ranges = range(0, no_of_process*chunk_size, chunk_size)
    processes = [ multiprocessing.Process(target=save_similar_docs, args= 
    (doc_id,client,fields,chunks,chunk_size)) for chunks in chunk_ranges]
    for prc in processes:
       prc.start()

def save_similar_docs(arguments):

     #This function process the args and saves the results to MongoDB. Does not 
     #return anything as the end result is directly stored.

下面是错误：

 File "H:/Desktop/Performance Improvement/With_Process_Pool.py", line 144, 
 in save_for_doc
   prc.start()

 File "C:\ProgramData\Anaconda3\lib\multiprocessing\process.py", line 105, 
 in start
  self._popen = self._Popen(self)

 File "C:\ProgramData\Anaconda3\lib\multiprocessing\context.py", line 223, 
 in _Popen
   return _default_context.get_context().Process._Popen(process_obj)

 File "C:\ProgramData\Anaconda3\lib\multiprocessing\context.py", line 322, 
 in _Popen
   return Popen(process_obj)

 File "C:\ProgramData\Anaconda3\lib\multiprocessing\popen_spawn_win32.py", 
 line 65, in __init__
reduction.dump(process_obj, to_child)

 File "C:\ProgramData\Anaconda3\lib\multiprocessing\reduction.py", line 60, 
 in dump
        ForkingPickler(file, protocol).dump(obj)

        TypeError: can't pickle _thread.lock objects

这个错误是什么意思？请解释一下，我该如何克服。

文档说您不能将客户端从主进程复制到子进程，您必须在分叉后创建连接。在 fork 进程后，客户端对象无法复制、创建连接。

在 Unix 系统上，多处理模块使用 fork() 生成进程。将 MongoClient 实例与 fork() 一起使用时必须小心。具体来说，MongoClient 的实例不得从父进程复制到子进程。相反，父进程和每个子进程必须创建自己的 MongoClient 实例。

http://api.mongodb.com/python/current/faq.html#id21 http://api.mongodb.com/python/current/faq.html#id21