Question

我试图评估多处理池中的多个进程，但一直遇到错误，我无法解决原因......下面是代码的简化版本：< / p>

class Object_1():

    def add_godd_spd_column()

        def calculate_correlations(arg1, arg2, arg3):
            return {'a': 1}

        processes = {}
        pool = Pool(processes=6)
        for i in range(1, 10):
            processes[i] = pool.apply_async(calculate_correlations,
                                            args=(arg1, arg2, arg3,))

        correlations = {}
        for i in range(0, 10):
            correlations[i] = processes[i].get()

这会返回以下错误：

Traceback (most recent call last):
  File "./02_results.py", line 116, in <module>
    correlations[0] = processes[0].get()
  File "/opt/anaconda3/lib/python3.5/multiprocessing/pool.py", line 608, in get
    raise self._value
  File "/opt/anaconda3/lib/python3.5/multiprocessing/pool.py", line 385, in 
_handle_tasks
    put(task)
  File "/opt/anaconda3/lib/python3.5/multiprocessing/connection.py", line 206, in send
     self._send_bytes(ForkingPickler.dumps(obj))
   File "/opt/anaconda3/lib/python3.5/multiprocessing/reduction.py", line 50, in dumps
    cls(buf, protocol).dump(obj)
AttributeError: Can't pickle local object 'SCADA.add_good_spd_column.<locals>.calculate_correlations

当我拨打以下电话时：相关性[0] .successful（）我收到以下错误：

Traceback (most recent call last):
  File "./02_results.py", line 116, in <module>
    print(processes[0].successful())
  File "/opt/anaconda3/lib/python3.5/multiprocessing/pool.py", line 595, in 
successful
    assert self.ready()
AssertionError

这是因为在调用.get（）之前，进程实际上还没有完成吗？正在评估的函数只返回一个绝对应该可以腌制的字典...

干杯，

Answer 1

发生错误是因为pickling a function nested in another function is not supported，并且multiprocessing.Pool需要将您作为参数传递的函数挑选到apply_async以便在工作进程中执行它。您必须将函数移动到模块的顶层，或使其成为类的实例方法。请记住，如果将其设为实例方法，则类本身的实例也必须是可选择的。

是的，调用successful()时出现断言错误是因为您在结果准备好之前调用它。 From the docs：

<强> successful()

返回调用是否完成而不引发异常。如果结果尚未准备就会提升AssertionError。

Python多处理池apply_async错误

1 个答案: