z = plt.axvline(longest, linestyle='--', color='black', alpha=0.5)
z.set_zorder(-1)
plt.xlim(0, complete_longest)
xvalues = list(range(0, complete_longest, 10))
xlabels = [str(x - longest) for x in xvalues]
plt.xticks(xvalues, xlabels)
Create a Diverging Stacked Bar Chart in matplotlib