setting tickslabel in matplotlib disables mouse cursor position

Question

Whenever I plot something in matplotlib, moving the mouse over the plot shows at the bottom the x and y position of the cursor. This is very convenient when exploring data.

Now, If I set the ticklabels to something else, the x position of the cursor at the bottom of the plot is empty, while the gui keeps track of the y position. Is there a way to keep getting the x position?

This is a simple example of this happening:

import numpy as np
fig, ax = plt.subplots()
x=np.linspace(0,np.pi)
y=np.sin(x)
ax.plot(x,y)
ax.set_xticks([0,np.pi/2,np.pi])
ax.set_xticklabels(['0','pi/2','pi'])
plt.show()

Answer 1

No, there is no easy way to do this.

When you set the labels with a list of strings you set the xaxis.major_formatter to be FixedFormatter (doc) which has some peculiar behavior to make it work (it always returns '', unless you give it a third argument which given when it labels the x-axis, but not otherwise). The marking of where the cursor is is generated using the major_formatter and when you call a FixedFormatter it returns '', which is what is displayed.

If you really want this, you have to write your own call back, see Color values in imshow for matplotlib? for a starting point. (or subclass axes and re-implement format_coord (around line 2903 in axes.py in current matplotlib master branch)