Python 2.7 理解python子进程popen异步

我的理解是subprocess.popen是一个异步调用，在调用后附加.wait（）将使其同步。第一次调用完成后，是否会执行第二次popen调用

proc1 = subprocess.Popen(first_command, stdout=subprocess.PIPE, shell=True)
proc2 = subprocess.Popen(second_command, stdin=proc1.stdout, stdout=self.fw, shell=True)

我试图确定何时需要使用wait（），以及为什么在上面的示例popen语句中使用wait（）会导致错误，例如：

proc1 = subprocess.Popen(first_command, stdout=subprocess.PIPE, shell=True).wait()  # throws exception
proc2 = subprocess.Popen(second_command, stdin=proc1.stdout, stdout=self.fw, shell=True).wait()  # seems ok

---

经过大量的尝试和错误，并重新阅读其他帖子和文档，这就是有效的方法

proc1 = subprocess.Popen(cmd1, stdout=subprocess.PIPE, shell=True)
# don't put wait here because of potential deadlock if stdout buffer gets full and we're waiting for proc2 to consume buffer then we're deadlocked
proc2 = subprocess.Popen(cmd2, stdin=proc1.stdout, stdout=self.fw, shell=True)
# ok to wait here
proc2.wait()
# ok to test return code after proc2 completes
if proc2.returncode != 0:
    print('Error spawning cmd2')
else:
    print('Success spawning cmd2')

希望这能帮助其他人