only vertical grid lines?


I used matplotlib to create a graphical representation of the boot
process of my Debian GNU/Linux system. The result can be found at

and especially in the (2400x1500 sized) picture

I have a question about matplotlib usage: I would like the picture to
have vertical grid lines at positions 1, 2, 3, 4, ..., not horizonzal
grid lines. On the horizontal x-Axis I would like to see labels at
positions 0, 5, 10, 15, ... and I would like to get rid of the labels
on the y-Axis. Is this possible? How do I do it?

All the best,