ax = fig.add_subplot(1, 1, 1)
ax.set_xlim(-50, 50)
ax.set_ylim(-75, 75)
x = [-50, 0, 50]
y = np.array([-50, 0, 0])
ax.fill_between(x, y - 30, y + 30)
ax.grid()
plt.show()
Matplotlib: draw lines with width given in data coordinates