如何使用 matplotlib 将主要和次要刻度标签精确对齐

Question

I have a graph with major tick labels the first day of months, and minor tick labels the other days of the month. If you look closely you can see that the day strings are not aligned. I would like to move minor labels a little bit down to align them with majors. or vice versa.

I don't want to make minor ticks bigger, or majors smaller

How would I do that?

This is the code piece, to generate the major/minor labels like in figure:

# draw canvas for x-ticks/labels
fig.canvas.draw()

# x-axis ticks/labels
x_minor_labels = [item for item in ax.xaxis.get_minorticklabels()]
for item in x_minor_labels:
    if int(item.get_text()) in (8, 15, 22, 29):
        item.set_visible(True)
    else:
        item.set_visible(False)

x_major_labels = [item for item in ax.xaxis.get_majorticklabels()]
x_major_labels[0].set_text(x_major_labels[0].get_text() + str(2021))
ax.set_xticks(ax.get_xticks().tolist())
ax.set_xticklabels(x_major_labels)

---

>>>x_minor_labels[0].get_position()
(18629.0, 0)
>>>x_major_labels[0].get_position()
(18628.0, 0)

Expected Outcome:

Answer 1

Labels are just text objects, so you can just set a new position with the set_position method.

major_labels = ax.xaxis.get_majorxticklabels()
_, y = major_labels[0].get_position()

for label in ax.xaxis.get_minorxticklabels():
     x, _ = label.get_position()
     label.set_position(x, y)

fig.canvas.draw()

Answer 2

I found out I can move minor labels via:

ax.get_xaxis().set_tick_params(which='minor', pad=5)

However, I am not sure setting pad=5 makes minor labels exactly next to major labels for all plots (for my case it works). Probably also depends on the figure size etc... So an eleganter solution should exist.