如果在子进程执行时执行 Ctrl+C，Python 是否总是引发异常？

给出以下代码：

try:
  subprocess.Popen(ExternalProcess, stdout=subprocess.PIPE,stderr=subprocess.PIPE, shell=True).communicate()
except KeyboardInterrupt:
  exit(0)

If during the execution of ExternalProcess(which is not a python script) one presses the Ctrl+C command, what exactly is going on?

Can I be sure for a 100% that in this scope, if I press the Ctrl+C, it will always get into the 'except' even if it happens during the execution of ExternalProcess?

还是取决于外部流程如何处理？

As far as I understand, once you fork/exec a process, it inherits the parent's process group http://en.wikipedia.org/wiki/Process_group. That means, that SIGINT (which is the result of Ctrl+C and the cause of KeyboardInterrupt) will be sent to both the child and the parent.

这是一个例子：

File a.py:

import subprocess

try:
    subprocess.Popen("python b.py".split()).communicate()
except KeyboardInterrupt:
    print "a.py got ctrl-c"

File b.py

try:
    while True: pass
except KeyboardInterrupt:
    print "b.py got ctrl-c"

现在运行它并停止：

> python a.py
^Cb.py got ctrl-c
a.py got ctrl-c