[英]python: concurrent.futures.as_completed printing results only after all the processes are completed
1)我正在嘗試使用 concurrentFutures 執行 8 個並行進程。 代碼按預期工作。 但是只有在所有過程完成后才會打印結果。 我希望在結果可用時立即打印結果(而不是在所有過程完成之后)。 我怎樣才能做到這一點?
2) “do_it” function 在 IDLE 環境中不打印任何內容,只有 main() function 中的打印命令在 IDLE window 上打印。但是“do_it”中的打印命令在線打印 python 編譯器 882347039197058 ( 86821) www.programiz.com/python-programming/online-compiler/ )。 為什么?
我在 Windows 操作系統上使用 python3.9.5。
import concurrent.futures
import time
def do_it(x):
print(f'sleeping for {x}')
start = time.perf_counter()
time.sleep(x)
end = time.perf_counter()
tTaken = round(end - start, 2)
return ['done sleeping', tTaken]
def main():
start = time.perf_counter()
with concurrent.futures.ProcessPoolExecutor() as executor:
delays = [1,2,3,4,5,6,7,8]
results = [executor.submit(do_it, x) for x in delays]
for f in concurrent.futures.as_completed(results):
[txt, duration] = f.result()
print(f'{txt} : time taken {duration}')
end = time.perf_counter()
tTaken = round(end - start, 2)
print(f'total time taken : {tTaken}')
if __name__ == '__main__':
main()
您只能在執行程序完成后才開始as_completed
。
嘗試在執行程序仍然存在時運行:
def main():
start = time.perf_counter()
print("Submitting jobs")
with concurrent.futures.ProcessPoolExecutor() as executor:
delays = [1, 2, 3, 4, 5, 6, 7, 8]
results = [executor.submit(do_it, x) for x in delays]
print("Running as_completed", flush=True)
for f in concurrent.futures.as_completed(results):
[txt, duration] = f.result()
print(f"{txt} : time taken {duration}", flush=True)
end = time.perf_counter()
tTaken = round(end - start, 2)
print(f"total time taken : {tTaken}")
這應該導致類似的結果:
Submitting jobs
sleeping for 1
sleeping for 2
sleeping for 3
Running as_completed
sleeping for 4
sleeping for 5
done sleeping : time taken 1.04
sleeping for 6
done sleeping : time taken 2.03
sleeping for 7
done sleeping : time taken 3.0
sleeping for 8
done sleeping : time taken 4.01
done sleeping : time taken 5.05
done sleeping : time taken 6.07
done sleeping : time taken 7.01
done sleeping : time taken 8.03
total time taken : 12.08
編輯
關於output子進程的缺失,這與Python如何在ms-windows上啟動新進程有關。 與 UNIX/POSIX 系統相反,文件句柄不會被子進程繼承。 因此,您不會在 ms-windows 上看到來自子進程的print
output。 猜測網上的python運行在UNIX/POSIX系統上。
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