如何在 Python 中同步运行命令

Question

我正在制作 DVD 翻录脚本，需要同步运行命令才能使我的脚本正常工作。我一直在尝试使用子流程但没有成功。此测试代码应运行至少 7 秒。

import subprocess
import time

start_time = time.time()

p1 = subprocess.Popen(['timeout', "2"], shell=False,
                     stdout=subprocess.PIPE, stderr=subprocess.DEVNULL)

p2 = subprocess.Popen(['timeout', "5"], shell=False,
                     stdout=subprocess.PIPE, stderr=subprocess.DEVNULL)

print(f"Finshed in {time.time() - start_time} Seconds")

Answer 1

使用.run() [1]

import subprocess
import time

start_time = time.time()
p1 = subprocess.run(['sleep', "2"])
p2 = subprocess.run(['sleep', "5"])
print(f"Finshed in {time.time() - start_time} Seconds")

[1]https://docs.python.org/3/library/subprocess.html#subprocess.run

Answer 2

可以使用Popen.wait方法，等待子进程终止：

import subprocess
import time

start_time = time.time()

p1 = subprocess.Popen(['sleep', "2"], shell=False,
                     stdout=subprocess.PIPE, stderr=subprocess.DEVNULL)
p1.wait()

p2 = subprocess.Popen(['sleep', "5"], shell=False,
                     stdout=subprocess.PIPE, stderr=subprocess.DEVNULL)
p2.wait()

print(f"Finshed in {time.time() - start_time} Seconds")

如果我运行这个：

(py39) Juans-MacBook-Pro:~ juan$ python -B stackoverflow.py
Finshed in 7.015462160110474 Seconds

注意，subprocess 文档建议您使用 subprocess.run 辅助函数，它会自动阻塞直到子进程终止。它返回一个subprocess.CompletedProcess 对象。所以：

import subprocess
import time

start_time = time.time()

result1 = subprocess.Popen(['sleep', "2"], shell=False,
                     stdout=subprocess.PIPE, stderr=subprocess.DEVNULL)

result2 = subprocess.run(['sleep', "5"], shell=False,
                     stdout=subprocess.PIPE, stderr=subprocess.DEVNULL)

print(f"Finshed in {time.time() - start_time} Seconds")

将是另一种方法。