human
Complete this python program:
def exe_exists(exe):
assistant
#Here is the Python program you requested.

    """Determine whether path/name refers to an executable.
    :param str exe: Executable path or name
    :returns: If exe is a valid executable
    :rtype: bool
    """
    def is_exe(path):
        'Determine    if    path    is    an    exe.'
        return (os.path.isfile(path) and os.access(path, os.X_OK))
    (path, _) = os.path.split(exe)
    if path:
        return is_exe(exe)
    else:
        for path in os.environ['PATH'].split(os.pathsep):
            if is_exe(os.path.join(path, exe)):
                return True
    return False