Vertical lines are great for showing spots where something happened on the x-axis.
Matplotlib provides the axes.vlines() method to plot vertical lines.
Here is the example
And here is the result.
Here you are! You now know how to plot a vertical line with Matplotlib.
More on plots
If you want to know more about how to add labels, plot different types of plots, etc... checkout the other articles I wrote on the topic, just here :