[英]error_callback in multiprocessing.Pool apply_async in Python 2?
[英]Python multiprocessing pool apply_async error
我正在嘗試評估多處理池中的許多進程,但仍然遇到錯誤,我無法解決原因......下面是代碼的簡化版本:
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()
這將返回以下錯誤:
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
當我調用以下內容:correlations [0] .successful()我收到以下錯誤:
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
這是因為在調用.get()之前,進程實際上沒有完成嗎? 正在評估的函數只返回一個絕對應該可以選擇的字典......
干杯,
發生錯誤是因為不支持在另一個函數中嵌套函數 ,並且multiprocessing.Pool
需要將您傳遞的函數作為apply_async
的參數進行apply_async
,以便在工作進程中執行它。 您必須將函數移動到模塊的頂層,或使其成為類的實例方法。 請記住,如果將其設為實例方法,則類本身的實例也必須是可選的。
是的,調用successful()
時出現斷言錯誤是因為你在結果准備好之前調用它。 來自文檔 :
successful()
返回是否完成調用而不引發異常。 如果結果未准備好,將引發
AssertionError
。
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