> File descriptors 0, 1, 2 are special: stdin, stdout and stderr file descriptors. You should use stdin, stdout, and stderr parameter of subprocess.

I finally find why `fd 0` is inherited. The reason is that os.dup2() has a parameter "inheritable" which defaults to True. Not because it's special stdin.

I still think this is a bug. If some one closes fd 0, then he reopens it. it will not be inherited.