ax2 = ax.twinx()
ax.yaxis.set_major_locator(mtick.LinearLocator(5))
ax2.yaxis.set_major_locator(mtick.LinearLocator(5))
ax.set_ylim(0, 15)
ax2.set_ylim(0, 1500)
ax.yaxis.grid(True, lw=7, color='g', ls='--')
ax2.yaxis.grid(True, color='k', ls='-', lw=3)
How to create equal number of primary and secondary y-axes ticks with matplotlib?