具体内容参见：https://docs.python.org/3/library/subprocess.html
大概来说，就是可以对应输入的命令产生一个进程，该进程实例内置如下方法。
| communicate(self, input=None, timeout=None)
| Interact with process: Send data to stdin. Read data from
| stdout and stderr, until end-of-file is reached. Wait for
| process to terminate. The optional input argument should be
| bytes to be sent to the child process, or None, if no data
| should be sent to the child.
|
| communicate() returns a tuple (stdout, stderr).
|
| kill = terminate(self)
|
| poll(self)
|
| send_signal(self, sig)
| Send a signal to the process.
|
| terminate(self)
| Terminates the process.
|
| wait(self, timeout=None, endtime=None)
| Wait for child process to terminate. Returns returncode
| attribute.
在windows系统中，kill是terminate方法的别名，在linux系统中，kill向进程发送SIGKILL信号，terminate方法向进程发送SIGTERM信号。