python - Windows 上的多处理中断

Question

我在 Linux 上使用 Python 进行开发，但从未真正在 Windows 上遇到过此类问题。我正在使用 multiprocessing 库来加速计算，这对我来说在 Linux 上非常有效。

然而，在 Windows 上，事情并不顺利:

 * [INFO] Parsing 1 file using 2 threads

Traceback (most recent call last):
  File "main.py", line 170, in <module>
    master = ParsingMaster(parser, list(input_file), output_list, threads=num_threads)
Traceback (most recent call last):
  File "main.py", line 39, in __init__
  File "<string>", line 1, in <module>
    self.input_process.start()
  File "C:\Python26\lib\multiprocessing\forking.py", line 342, in main
  File "C:\Python26\lib\multiprocessing\process.py", line 104, in start
        self._popen = Popen(self)
self = load(from_parent)
  File "C:\Python26\lib\multiprocessing\forking.py", line 239, in __init__
  File "C:\Python26\lib\pickle.py", line 1370, in load
    dump(process_obj, to_child, HIGHEST_PROTOCOL)
  File "C:\Python26\lib\multiprocessing\forking.py", line 162, in dump
    ForkingPickler(file, protocol).dump(obj)
  File "C:\Python26\lib\pickle.py", line 224, in dump
    return Unpickler(file).load()
    self.save(obj)
 File "C:\Python26\lib\pickle.py", line 858, in load
  File "C:\Python26\lib\pickle.py", line 331, in save
    self.save_reduce(obj=obj, *rv)
  File "C:\Python26\lib\pickle.py", line 419, in save_reduce
    dispatch[key](self)
  File "C:\Python26\lib\pickle.py", line 880, in load_eof
    save(state)
  File "C:\Python26\lib\pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
    r aise EOFError
 File "C:\Python26\lib\pickle.py", line 649, in save_dict
EOFError
    self._batch_setitems(obj.iteritems())
  File "C:\Python26\lib\pickle.py", line 681, in _batch_setitems
    save(v)
  File "C:\Python26\lib\pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "C:\Python26\lib\multiprocessing\forking.py", line 40, in dispatcher
    self.save_reduce(obj=obj, *rv)
  File "C:\Python26\lib\pickle.py", line 401, in save_reduce
    save(args)
  File "C:\Python26\lib\pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "C:\Python26\lib\pickle.py", line 548, in save_tuple
    save(element)
  File "C:\Python26\lib\pickle.py", line 331, in save
    self.save_reduce(obj=obj, *rv)
  File "C:\Python26\lib\pickle.py", line 419, in save_reduce
    save(state)
  File "C:\Python26\lib\pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "C:\Python26\lib\pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "C:\Python26\lib\pickle.py", line 681, in _batch_setitems
    save(v)
  File "C:\Python26\lib\pickle.py", line 306, in save
    rv = reduce(self.proto)
  File "C:\Python26\lib\multiprocessing\managers.py", line 458, in __reduce__
    return type(self).from_address, \
AttributeError: type object 'SyncManager' has no attribute 'from_address'

我在 Windows 7 上对 Python 2.6 和 2.7 进行测试，一遍又一遍地遇到同样的错误。有人知道这是什么意思吗？

Answer 1

Windows 有限制，以下是您所看到的错误的相关部分:

Since Windows lacks os.fork() it has a few extra restrictions:

更多的可 pickle

Ensure that all arguments to Process.__init__() are picklable. This means, in particular, that bound or unbound methods cannot be used directly as the target argument on Windows — just define a function and use that instead.

Also, if you subclass Process then make sure that instances will be picklable when the Process.start() method is called.

这意味着某些东西作为参数传递给 Process.__init__() isn't able to be pickled or unpickled (Python 中的序列化)。什么是 SyncManager 它提示无法在该对象上找到属性 AttributeError: type object 'SyncManager' has no attribute 'from_address'，这可能是你的根本原因. SyncManager 对象真的可以 pickle 吗，does it meet the pickle rules ？

如果您从 command line on Windows, you can't do that 运行它显然。

不要那样做。将代码保存在一个文件中，然后使用以下命令从该文件运行它:

python myfile.py

这将解决您的问题。