Matplot lib : scalling of the axes on bar plot
Use plt.xticks - https://matplotlib.org/3.1.1/api/_as_gen/matplotlib.pyplot.xticks.html.
One may to xticks np.arange(len(cluster.clusters)) as an argument
And for yticks it works in a same fashion -if you pass np.arange(int(max(cluster_sizes))), there will be integer ticks along the y-axis