Change ticks number on a plot in matplotlib

# Create your ticker object with M ticks
M = 3
yticks = ticker.MaxNLocator(M)

# Set the yaxis major locator using your ticker object. You can also choose the minor
# tick positions with set_minor_locator.
ax.yaxis.set_major_locator(yticks)

References
https://stackoverflow.com/questions/27425974/change-ticks-number-on-a-subplot