Instalando aplicativo usando python-apt

appinstall.py

#!/usr/bin/env python
# aptinstall.py

import apt
import sys

pkg_name = "firefox"

cache = apt.cache.Cache()
cache.update()

pkg = cache[pkg_name]
if pkg.is_installed:
    print "{pkg_name} ja esta instalado".format(pkg_name=pkg_name)
else:
    pkg.mark_install()

    try:
        cache.commit()
    except Exception, arg:
        print >> sys.stderr, "Desculpa, a instalacao do pacote falhou [{err}]".format(err=str(arg))