Comment on this script. Possible error in communication with list arg between functions

[Phoe6]

Hi all,
         Part of my script is to check for pre-requisite rpms to be
installed.
If its installed, I just display the rpm version as in rpm database,
otherwise I output a message saying:
' rpm is not installed' and collect the rpm name in a list
(notInstalled).
At the end if the len(notInstalled) is greater than 0 then I display
them all asking it to be installed and exit the program.
My Script is below:
-------
#!/usr/bin/env python
import os
import sys



notInstalled = []



def checkForRpm(rpmname):
        ''' Check for the presence of the RPM. '''
        cin,cout,cerr = os.popen3('rpm -q ' + rpmname)
        output = cout.read()
        global notInstalled
        if len(output) <= 0:
                print rpmname + ' not installed.'
                notInstalled.append(rpmname)
        else:
                print output



def preReqCheckRpms():
        ''' Check for the required RPMS '''
        listOfRpms =
['firefox','senthil','binutils','gcc','cpp','glibc-devel','glibc-headers','glibc-kernheaders','compat-db','compat-gcc','compat-gcc-c++','compat-libstdc++','compat-libstdc++-devel','gnome-libs','openmotif21','setarch']



        for eachRpm in listOfRpms:
                checkForRpm(eachRpm)
        global notInstalled
        if len(notInstalled) > 0:
                print 'The following RPMS are not installed:'
                for eachRpm in notInstalled:
                        print eachRpm
                print 'Please install them for the installation to
continue.'
                sys.exit(-1)






def main():
        preReqCheckRpms()



if __name__ == '__main__':
        main()
----

* This is NOT Working.
* notInstalled.append(rpmname) is not taking effect in
checkForRpm(rpmname)
* I dont know how to communicate the notInstalled list to
preReqCheckRpms.

-- 
Senthil