choropleth with custom bins

from matplotlib.colors import LinearSegmentedColormap

bins = [0,1]

# Maps values to a bin.
# The mapped values must start at 0 and end at 1.
def bin_mapping(x):
    for idx, bound in enumerate(bins):
        if x < bound:
            return idx / (len(bins) - 1.0)

# Create the list of bin labels and the list of colors 
# corresponding to each bin
bin_labels = [idx / (len(bins) - 1.0) for idx in range(len(bins))]
color_list = ['#edf8fb', '#b30000']

# Create the custom color map
cmap = LinearSegmentedColormap.from_list('mycmap', 
                                         [(lbl, color) for lbl, color in zip(bin_labels, color_list)])
for year in range(1990, 2017):
    plot_col="RATIO"+str(year)
    counties['Bin_Lbl'] = counties[plot_col].apply(bin_mapping)
    mpl.pyplot.savefig(str(year) + 'map.png')