Python，使用subprocess.Popen进行linux命令行调用？我得到“[Errno 2]没有这样的文件或目录”

I'm trying to follow the info I can find about subprocess.Popen as I want to make a linux command line call.. I am trying as below but am getting the error "[Errno 2] No such file or directory". I'm not trying to open a file so I don't understand this error, and it works fine (although with other issues relating to waiting for the process to finish when I don't want it to) when I use a regular os.popen.I'm trying to follow the info I can find about