def iqr(series):
    """
    Extract inter-quantile range
    (25%-75%)

    Input
    ---
        series : pandas series

    Returns
    ---
        inter-quantile range
        (25-75%)
    """
    Q1 = series.quantile(0.25)
    Q3 = series.quantile(0.75)
    IQR = Q3 - Q1
    return IQR