def liststr(l):
    """
    Concise string representation of iteratable
    """
    s = None
    if hasattr(l, '__iter__') and not isinstance(l, str):
        if len(l) == 0:
            s = 'None'
        elif len(l) == 1:
            s = str(l[0])
        else:
            s = '{}...{}'.format(l[0], l[-1])
    else:
        s = l
    return s
