Python线程池执行器未并行运行

Question

Python线程池执行器不是并行运行的，它正在按顺序调用多维数据集方法并等待完成，

其中我需要运行20个并行线程

from concurrent.futures import ThreadPoolExecutor
from time import sleep
def cube(x):
sleep(2)
print(f'Cube of {x}:{x*x*x}')
count = 0
while True:
with ThreadPoolExecutor(max_workers=20) as exe:
exe.submit(cube,2)
count += 1
if count > 50:
break   

Answer 1

"用"；语句对ThreadPoolExecutor使用__enter__方法，它此时初始化线程池。因此，对于线程池中的函数执行，我们应该在"内部使用它；用"；陈述

with ThreadPoolExecutor(max_workers=20) as exe:  # for default it will be number of os.cpu_count()
futures = []
for i in range(50):
futures.append(executor.submit(cube, i))
for future in concurrent.futures.as_completed(futures):
print(future.result())

Answer 2

我想想要这样的东西：

from concurrent import futures
from time import sleep
THREADS = 20
def cube(x):
sleep(2)
res = x*x*x
print(f'Cube of {x}:{res}')
return res
with futures.ThreadPoolExecutor(max_workers=THREADS) as exe:
jobs = {exe.submit(cube, i): i for i in range(THREADS)}
for job in futures.as_completed(jobs):
try:
data = job.result()
except Exception as exc:
print('%r generated an exception: %s' % (jobs[job], exc))
else:
print(f"Result of thread {jobs[job]}: {data})")

输出：

Cube of 2:8
Cube of 1:1
Cube of 3:27
Cube of 0:0
Cube of 4:64
Result of thread 2: 8)
Result of thread 1: 1)
Result of thread 0: 0)
Result of thread 4: 64)
Cube of 5:125
Cube of 6:216
Cube of 8:512
Cube of 14:2744
Cube of 12:1728
Cube of 17:4913
Result of thread 3: 27)
Cube of 13:2197
Cube of 7:343
Cube of 16:4096
Cube of 15:3375
Cube of 18:5832
Cube of 11:1331
Cube of 9:729
Cube of 19:6859
Cube of 10:1000
Result of thread 5: 125)
Result of thread 6: 216)
Result of thread 8: 512)
Result of thread 14: 2744)
Result of thread 12: 1728)
Result of thread 17: 4913)
Result of thread 13: 2197)
Result of thread 7: 343)
Result of thread 16: 4096)
Result of thread 15: 3375)
Result of thread 18: 5832)
Result of thread 11: 1331)
Result of thread 10: 1000)
Result of thread 19: 6859)
Result of thread 9: 729)