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

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.

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()