I have a usage question / maybe API enhancement request about _ipython_display_. I noticed today that objects defining a _ipython_display_ method don't seem to be able to trigger the Out[n] machinery for the output of a cell. Here's an example notebook Notice that the In[5] doesn't have an Out[5].

Is there any way in _ipython_display_ to say "treat this one as the return value". Should IPython treat the highest-priority one as the return value?

This came up in a pandas issue pandas-dev/pandas#16168 (comment)