import matplotlib.pyplot as plt
fig, axes = plt.subplots(nrows=2, subplot_kw=dict(aspect=1))
axes[0].plot(list(range(1, 4)))
axes[1].plot(list(range(10, 40, 10)), list(range(1, 4)))
for ax in axes:
    ax.annotate('Test', xy=(1, 0), xycoords='axes fraction', fontsize=16,
        xytext=(0, -15), textcoords='offset points', ha='right', va='top')
plt.show()
Python/Matplotlib - How to put text in the corner of equal aspect figure