def dsname(exp='xpptut15', run='0001') :
    """Returns (str) control file name, e.g. 'exp=xpptut15:run=1' for (str) exp and (str) of (int) run
    """
    if   isinstance(run, str) : return 'exp=%s:run=%s' % (exp, run.lstrip('0'))
    elif isinstance(run, int) : return 'exp=%s:run=%d' % (exp, run)
    else : return None