Pythonic way to check if a package is installed or not

Question

Pythonic way to check list of packages installed in Centos/Redhat?

In a bash script, I\'d do:

 rpm -qa | grep -w packagename

Answer 1

import os

present=0
notpresent=0
f3=open('INSTALLED.log','w')
f2=open('NOTINSTALLED.log','w')

f1=open('installed_packagelist.log','w')

var = os.popen("rpm -qa --queryformat '[%{NAME}\n]'").read()
f1.write(var)


lines = [line.rstrip('\n') for line in open('installed_packagelist.log')]

for index in range(len(lines)):
 contents = lines[index]
 test_str = "rpm -V " + contents
 var = os.system(test_str)
 if (var == 0):
  print contents + "file present"
  present = present +1
  f3.write(contents)

 else:
  print contents + "file not present"
  notpresent = notpresent + 1
  f2.write(contents)  

print present
print notpresent

f2.close()
f3.close()

f3=open('INSTALLED.log','r')
f2=open('NOTINSTALLED.log','r')


data=f3.read()
print data

print       "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++"

data=f2.read()
print data