Plot a vertical line using matplotlib

Question

I would like to draw a vertical line with Matpotlib and I\'m using axvline, but it doesn\'t work.

import sys
import matplotlib
matplotlib.use(\         


        

Answer 1

Your example is not self contained, but I think you need to replace:

plt.axvline(x=4)

with:

ax.axvline(x=4)

You are adding the line to an axis that you are not displaying. Using plt. is the pyplot interface which you probably want to avoid for a GUI. So all your plotting has to go on an axis like ax.