def izipcols(df, cols, index=False):
    """Return an iterator to go through rows of Pandas.DataFrame
    (Much faster than DataFrame.rows() which involves instantiation of Series objects)

    Args:
        df: DataFrame
        cols: list of column names
        index: if True, includue index at the beginning (default False)
    """
    if index:
        l = [df.index]+[df[x] for x in cols]
    else:
        l = [df[x] for x in cols]
    #return izip(*l) # python2
    return zip(*l)