th = np.linspace(0, 2 * np.pi, 64)
y = np.sin(th)
ax = plt.gca()
lin, = ax.plot(th, y, lw=5)
mark, = ax.plot(th, y, marker='o', alpha=0.5, ms=10)
ax.legend([(lin, mark)], ['merged'])
plt.draw()
Matplotlib - How to make the marker face color transparent without making the line transparent