Matplotlib: Labels on projection plot grid lines similar to clabel()

Question

I'm doing a bunch of work with various spherical projection plots using the Astropy WCS package, and have run into some frustrations concerning grid lines. As grid lines do not always intersect with the image bounding box or multiple intersect at the same place, they can go unlabeled or have their labels rendered illegible. I would like to be able to insert grid line labels in each line, much akin to the matplotlib.pyplot.clabel() function applied to contour plots, as in this matplotlib example. I can't embed the image as I am a new user; my apologies.

I know I can place labels using text(), figtext(), or annotate(), but since clabel() works I figure the functionality already exists, even if it hasn't been applied to grid lines. Projection plotting aside, does anyone know a way that in-line grid line labels akin to clabel() can be applied to grid lines on a plain rectangular plot?

Answer 1

To annotate the gridlines, you may use the positions of the major ticks (as those are the positions at which the gridlines are created).

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(0,10)
y = np.sin(x)*10

fig, ax = plt.subplots()
ax.plot(x,y)
ax.grid()

for xi in ax.xaxis.get_majorticklocs():
    ax.text(xi,0.8, "{:.2f}".format(xi), clip_on=True, ha="center",
            transform=ax.get_xaxis_transform(), rotation=90,
            bbox={'facecolor':'w', 'pad':1, "edgecolor":"None"})
for yi in ax.yaxis.get_majorticklocs():
    ax.text(0.86,yi, "{:.2f}".format(yi), clip_on=True, va="center",
            transform=ax.get_yaxis_transform(), 
            bbox={'facecolor':'w', 'pad':1, "edgecolor":"None"})

plt.show()