Run a linux system command as a superuser, using a python script

[madhav]

I have got postfix installed on my machine and I am updating on of its
configuration files programmatically(using python)(on some action).
Since any change in the configuration needs a reload, I need to reload
postfix to reflect the latest change. How can I do that in a python
script. Precisely, I have something like this:

import subprocess
subprocess.Popen('sudo /etc/init.d/postifx reload')

Since this script should be run in no-human environment(on the fly), I
cant supply the sudo password or even root password(if needed). Even
sudo doesn't have a flag to input the password for the command at the
first shot. How do I do this?