fig.set_size_inches([8.0, 12.0])
ax = fig.add_subplot(111)
ax.plot([1, 1, 2], [3, 4, 5], 'ro-')
ax1 = fig.add_subplot(212)
ax1.plot([2, 3, 4], [8, 9, 11], 'bs-')
fig.subplots_adjust()
Programmatically grow a figure in matplotlib