python - Colorbar offsetText (scientific base multiplier) move from top to bottom of colorbar

Question

I'm losing my wits here with this 'simple' problem:

In the colorbar (illustrated in picture) in matplotlib I need to move offsetText (base multiplier) from top of the colorbar to bottom.

Code that I'm using for this plot is (using gridspec):

f.add_subplot(ax12)

ax10 = plt.Subplot(f, gs00[1, 0])
cb = plt.colorbar(h3,cax=ax10)
cb.formatter.set_scientific(True)
cb.formatter.set_powerlimits((0,0))
cb.ax.yaxis.offsetText.set(size=6)
cb.update_ticks()

ax10.yaxis.set_ticks_position('left')
ax10.tick_params(labelsize=6)
f.add_subplot(ax10)

Thanks in advance! (Btw, Python version = 2.7.6, matplotlib version = 1.3.1 - upgrading currently not an option until I finish current project)

Answer 1

It's in general not possible to change the position of the offsetText label. This would still be an open issue.

A solution can therefor be to overwrite the yaxis' _update_offset_text_position method to position the offsetText on the bottom of the yaxis.

import matplotlib.pyplot as plt
import types

def bottom_offset(self, bboxes, bboxes2):
    bottom = self.axes.bbox.ymin
    self.offsetText.set(va="top", ha="left")
    self.offsetText.set_position(
            (0, bottom - self.OFFSETTEXTPAD * self.figure.dpi / 72.0))

fig, ax = plt.subplots()
im = ax.imshow([[1e5,2e5],[0.1e5,1e5]])
cb = plt.colorbar(im)
cb.formatter.set_scientific(True)
cb.formatter.set_powerlimits((0,0))

def register_bottom_offset(axis, func):
    axis._update_offset_text_position = types.MethodType(func, axis)
register_bottom_offset(cb.ax.yaxis, bottom_offset)

cb.update_ticks()

plt.show()

If the colorbar is positioned on the left side of the plot the following might look better:

self.offsetText.set(va="top", ha="right")
self.offsetText.set_position(
            (1, bottom - self.OFFSETTEXTPAD * self.figure.dpi / 72.0))