I'd guess the normal way to access that info would be ax.xaxis.get_gridlines()[0].get_visible()? (loop over the gridlines and decide what you want to do if you want to additionally handle the case of not all gridlines having the same visibility)

I'm not sure I'd want a new method, though (what would we do if the user manually switched the visibility of only a subset of gridlines?).

OK, that seems public enough to me. OTOH I don't see a way to get the minor gridlines from this? So maybe add a get_gridlines(which='minor'/'major'/'both')? Or a new get_minorgridlines?

I guess just ax.xaxis.get_minor_ticks()[0].gridline.get_visible()...

Cross ref:

• Fix compatibility with matplotlib 3.3.3 gwpy/gwpy#1278
• 'XAxis' object has no attribute '_gridOnMajor' plotly/plotly.py#2913
• XAxis' object has no attribute '_gridOnMajor mpld3/mpld3#479
• Fix 2 Matplotlib errors mpld3/mplexporter#60

Some downstream packages use that approach: https://github.com/mwaskom/seaborn/blob/2717408b564994002fe08f72ba2dd7e1acf359b6/seaborn/distributions.py#L827...L830

IMO Axis.grid_on is not very obviously a "status checker" method vs a "do an action" method...