def plot_piechart(data, column_numbers, column_index):
    """
    Plots a preformated pie chart
        - data: dataframe
        - column_values: column name for quantitative values
        - column_index: column name for qualitative values
    """

    ''' colormaps:  https://matplotlib.org/examples/color/colormaps_reference.html
                    https://matplotlib.org/tutorials/colors/colormaps.html#kovesi-colormaps'''
    colors = plt.cm.GnBu(np.linspace(0.6, 1, len(data)))
    
    maxdata = max(data[column_numbers])
    mindata = min(data[column_numbers])
    explode = []
    
    for v in data[column_numbers]:
        if v == maxdata:
            explode.append(0.15)
        elif v == mindata:
            explode.append(0)
        else:
            explode.append(0)
    
    plt.pie(data[column_numbers], counterclock=False, shadow=False, \
    autopct='%.1f', textprops={'color':"white"}, explode=explode)

    circle=plt.Circle( (0,0), 0.3, color='white')
    plt.gca().add_artist(circle)
    
    plt.legend(labels=data[column_index],bbox_to_anchor=(1,0.5), \
    loc="center right", fontsize=10, 
           bbox_transform=plt.gcf().transFigure)
    
    plt.rcParams['axes.prop_cycle'] = cycler(color=colors)
    
    return(plt.show())