def isunique(table, field):
    """
    Return True if there are no duplicate values for the given field(s),
    otherwise False. E.g.::

        >>> import petl as etl
        >>> table1 = [['foo', 'bar'],
        ...           ['a', 1],
        ...           ['b'],
        ...           ['b', 2],
        ...           ['c', 3, True]]
        >>> etl.isunique(table1, 'foo')
        False
        >>> etl.isunique(table1, 'bar')
        True

    The `field` argument can be a single field name or index (starting from
    zero) or a tuple of field names and/or indexes.

    """

    vals = set()
    for v in itervalues(table, field):
        if v in vals:
            return False
        else:
            vals.add(v)
    return True
Return True if there are no duplicate values for the given field(s),
    otherwise False. E.g.::

        >>> import petl as etl
        >>> table1 = [['foo', 'bar'],
        ...           ['a', 1],
        ...           ['b'],
        ...           ['b', 2],
        ...           ['c', 3, True]]
        >>> etl.isunique(table1, 'foo')
        False
        >>> etl.isunique(table1, 'bar')
        True

    The `field` argument can be a single field name or index (starting from
    zero) or a tuple of field names and/or indexes.