Change file owner user/group by either username/groupname or numeric ID

chown_by_name.py

#!/usr/bin/python                                                                                                 
import os
import pwd
import grp


def chown_by_name(path, user, group = None):
    """Chowns file based on username and groupname
       If group name is left blank, group is preserved
    """
    try:
        uid = int(user)
    except: 
        t = pwd.getpwnam(user)
        uid = t[2]
    
    if group == None:
        gid = os.stat(path)[5]
    else:
        try:
            gid = int(group)
        except:
            t = grp.getgrnam(group)
            gid = t[2]

    os.chown(path, uid, gid)