It is still possible to use the regular static backend after this commit, as long as don't explicitly set it to WebAgg.

I can't reproduce this. I suspect that this probably has something to do with a version mismatch of either IPython or Tornado.

>>> import tornado
>>> tornado.version
'3.1'
>>> import IPython
>>> IPython.__version__
'0.13.2'

It seems related to the IPython version: the following snippet

import matplotlib.pyplot as plt
plt.switch_backend('webAgg')
plt.plot([1,2,3], 'o')
plt.show()

works for me in both IPython 0.13.2 and 1.0.0

However, the new %matplotlib inline syntax introduced in IPython 1.0 is broken from 27482be onwards. From the traceback, it seems that MPL is trying to use the WebAgg backend, even though I never set the webAgg backend (see the gist)

I upgraded to IPython 1.0, and tried exactly what's in your gist, but still couldn't reproduce.

However (and this is puzzling, but at least it gets us somewhere), if I type:

plt.<TAB>pl<TAB>([1,2,3])

i.e., trigger autocomplete at some point while entering the content, I get the same traceback as in the gist.

Ok, I think I have a fix. Would you mind testing it?

The gist now runs for me, and (correctly) uses IPython's inline backend.