List installed pkgs (smaller than the "yum list" snippet).

# This uses rpm directly:
import rpm

ts = rpm.TransactionSet()
ts.setVSFlags((rpm._RPMVSF_NOSIGNATURES|rpm._RPMVSF_NODIGESTS))
for hdr in ts.dbMatch(): # No sorting
    if hdr['name'] == 'gpg-pubkey':
        continue
    else:
        print '%s-%s:%s-%s.%s' % (hdr['name'],
                                  hdr['epochnum'],hdr['version'],hdr['release'],
                                  hdr['arch'])



# Via. yum
import yum
yb = yum.YumBase()
yb.conf.cache = 1
for pkg in sorted(yb.pkgSack.returnPackages()):
    print pkg, pkg.repo