subprocess
模块方法：
call()
check_call()
check_output()
以上三个方法用于创建一个子进程，父进程等待子进程结束。若shell = true, 则shell 参数以字符串形式给出，否则，则以序列的形式给出。
Popen 对象：
child = Popen((args, bufsize=-1, executable=None, stdin=None, stdout=None, stderr=None, preexec_fn=None, close_fds=True,shell=False,
cwd=None, env=None, universal_newlines=False, startupinfo=None, creationflags=0, restore_signals=True,
start_new_session=False, pass_fds=()))
Use communicate() rather than .stdin.write, .stdout.read or .stderr.read to avoid deadlocks due to any of the other OS pipe buffers filling up and blocking the child process.
对象方法：
child.poll() # 检查子进程状态
child.kill() # 终止子进程
child.send_signal() # 向子进程发送信号
child.terminate() # 中止子进程
child.wait() #等待子进程终止
child.communicate() #和子进程交互