Python Concurrent.Futures ProcessPool Executor错误输出
Python Concurrent.Futures ProcessPool Executor错误输出
提问于 2021-10-07 15:49:55
我正在尝试使用ProcessPoolExecutor()来运行一些函数，但是我无法理解如何从with中获取函数的返回。
def threaded_upload(i):
time.sleep(2)
if i == 0:
k = 10
elif i == 2:
k = i*i
else:
k = -99
return [k]
def controller():
if __name__ == "__main__":
futures = []
with ProcessPoolExecutor() as pool:
for paso in range(4):
futuro_i = pool.submit(threaded_upload,paso)
wth=[futuro_i.result()]
futures.append(futuro_i)
wait(futures, return_when=ALL_COMPLETED)
merged_list = []
for future in futures:
for valor in future.result():
merged_list.append(valor)
Lista_Final = merged_list
wait(futures, return_when=ALL_COMPLETED)
return Lista_Final
print(controller())代码的输出是: None 10，-99，4，-99
我不知道为什么？“等待”似乎也不会等到所有函数都执行完。
老实说，我已经读了几天了，但对concurrent.futures或多进程的描述比我目前的知识更高级。
任何澄清都将不胜感激。提前谢谢。
回答 1
Stack Overflow用户
发布于 2021-10-16 08:47:29
首先提交作业，然后等待结果。也可以返回整数而不是list，然后跳过内部loop
test.py:
import random
import time
from concurrent.futures import ProcessPoolExecutor, wait
def worker(i):
t = random.uniform(1, 5)
print(f"START: {i} ({t:.3f}s)")
time.sleep(t)
if i == 0:
k = 10
elif i == 2:
k = i * i
else:
k = -99
print(f"END: {i}")
return k
def main():
futures = []
with ProcessPoolExecutor() as pool:
for i in range(4):
future = pool.submit(worker, i)
futures.append(future)
results = []
done, pending = wait(futures) # ALL_COMPLETED is the default value
for future in done:
results.append(future.result())
print(results)
if __name__ == "__main__":
main()测试：
$ python test.py
START: 0 (1.608s)
START: 1 (1.718s)
START: 2 (1.545s)
START: 3 (1.588s)
END: 2
END: 3
END: 0
END: 1
[10, -99, 4, -99]页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/69484176
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