Both functions use the os.path.split(path) function to split the pathname path into a pair; (head, tail).
The os.path.dirname(path) function returns the head of the path.
E.g.: The dirname of '/foo/bar/item' is '/foo/bar'.
The os.path.basename(path) function returns the tail of the path.
E.g.: The basename of '/foo/bar/item' returns 'item'
From: http://docs.python.org/3/library/os.path.html#os.path.basename