522 def username(uid=None):

   523     """Return the name of the user with the given uid.

   524 

   525     If uid is None, return the name of the current user."""

   526     try:

   527         import pwd

   528         if uid is None:

   529             uid = os.getuid()

   530         try:

   531             return pwd.getpwuid(uid)[0]

   532         except KeyError:

   533             return str(uid)

   534     except ImportError:

   535         return None

   536 

   537 def groupname(gid=None):

   538     """Return the name of the group with the given gid.

   539 

   540     If gid is None, return the name of the current group."""

   541     try:

   542         import grp

   543         if gid is None:

   544             gid = os.getgid()

   545         try:

   546             return grp.getgrgid(gid)[0]

   547         except KeyError:

   548             return str(gid)

   549     except ImportError:

   550         return None

   551