from subprocess import call
call(["ls", "-l"])

The advantage of subprocess vs system is that it is more flexible (you can get the stdout, stderr, the "real" status code, better error handling, etc...). I think os.system is deprecated, too, or will be:

http://docs.python.org/library/subprocess.html#replacing-older-functions-with-the-subprocess-module

For quick/dirty/one time scripts, os.system is enough, though