Is there any way to excute a command as a specific user in Python?
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As far as I kown, there are about 3 ways to excute a system command in Python:

1. `os.system(command) -> exit_status`

2. `os.popen(command [, mode='r' [, bufsize]]) -> pipe`

3. `commands.getoutput(command)-> string`

Now I need to control the excutor of a system command, beside the way like: 

   `os.system('su xxx;' + command)`

is there any other more elegant way to reach the same effect?