import pwd
myGroupId = pwd.getpwnam(username).pw_gid

import os
myGroupIds = os.getgroups()

id -Gn `whoami`

#!/usr/bin/env python
import grp, pwd 
user = "myname"
groups = [g.gr_name for g in grp.getgrall() if user in g.gr_mem]
gid = pwd.getpwnam(user).pw_gid
groups.append(grp.getgrgid(gid).gr_name)
print groups