How to add vertical tick marks to all horizontal grid lines in matplotlib?

Question

I would like to know if it is possible to have the x-ticks (major and minor) displayed on all horizontal grid lines of a matplotlib graph.

I have a large line graph with many mostly vertical lines (see image). I use horizontal grid lines because they do not interfere with the data. But I do not want to use vertical grid lines because the graph is already quite busy.

What I would like is to have major and minor vertical tick marks shown on every horizontal grid line (as if I had shown all vertical grid lines, but erased everywhere that wasn't crossing a horizontal grid line).

Is this possible?

Here is a sample image that needs the vertical ticks added to every grey horizontal grid line.

Answer 1

There's no easy function that will do this for you.

One possible solution is to plot vertical lines using vlines at the points where the xticks are, using the y ticks location as the maximum y value and subtracting a small offset for the y minimum. A simple example:

import matplotlib.pyplot as plt

fig, ax = plt.subplots()

ax.plot([1,2,3], [1,2,3])
ax.set_yticks([1, 2, 2.5])
ax.set_xticks([1, 1.5, 2, 2.5, 3])
ax.grid(axis="y")

yticks = ax.get_yticks()
xticks = ax.get_xticks()

for ytick in yticks:
    for xtick in xticks:
        ax.vlines(xtick, ytick-0.05, ytick, linewidth=0.5)

plt.show()