python - How do I animate the ticks on the x-axis?

Question

I have a matplotlib axes instance inside which I'm animating an AxesImage via blitting.

What I'd like to do is animate the ticks on the x-axis as well. I am updating the data on the AxesImage (and subsequently) drawing its artist quite frequently, and on each update I'd like to move one extra tick placed to highlight the position of something. This is what I'm doing right now:

axis = axes.get_xaxis
im.set_data(new_data)
axis.set_ticks([10,20,30,x,t])
axis.set_ticklabels(["p", "u", "z", "z", "i"])
axes.draw_artist(im)
axes.draw_artist(axis)

While I see the ticks correctly updating, the labels are not. I think that the axes bbox does not include the axes, is this possible? If so, how can I animate it? Should I copy and restore from somewhere else?

Answer 1

The axes bbox doesn't include anything outside of the "inside" of the axes (e.g. it doesn't include the tick labels, title, etc.)

One quick way around this is to just grab the entire region of the figure when you're blitting. (E.g. background = canvas.copy_from_bbox(fig.bbox))

This can cause problems if you have multiple subplots and only want to animate one of them. In that case, you can do something along the lines of background = canvas.copy_from_bbox(ax.bbox.expanded(1.1, 1.2)). You'll have to guesstimate the ratios you need, though.

If you need the exact extent of the tick labels, it's a bit trickier. The easiest way is to iterate through the ticklabel objects and get the union with ax.bbox. You can make this a one-liner: ax.bbox.union([label.get_window_extent() for label in ax.get_xticklabels()]).

At any rate, one of those three options should do what you need, I think.