In my virtual environment, there happens to be installed IPython package. It wasn't installed by myself, it's merely a transitive dependency of some another package. It's neither intended to be used, nor is actually used by my project. However, mere presense of the IPython package, due to the over-simplistic decision code in this module (io._renderers) leads to drastic behavior change in Plotly.py: calling Figure.repr_html() causes lots of JS garbage to be printed on terminal (by common sense, this should be a side-effects free function, only returning a value). On a higher level, this breaks natural Plotly.py integration in frameworks like Shiny.py (because again, instead of HTML representation being returned for a framework to process, parts of that representation are dumped on terminal).

The real underlying issue is that Plotly.py should not force-import any "optional" packages behind users' back. However, this is a deeper issue requiring consideration and will be reported separately. This patch is a quick solution for the problem describe above.

From interactive session:

>>> import IPython
>>> IPython.get_ipython().__class__.__name__
'NoneType'

Code PR

• I have read through the contributing notes and understand the structure of the package. In particular, if my PR modifies code of plotly.graph_objects, my modifications concern the codegen files and not generated files.
• I have added tests (if submitting a new feature or correcting a bug) or
  modified existing tests.
• For a new feature, I have added documentation examples in an existing or
  new tutorial notebook (please see the doc checklist as well).
• I have added a CHANGELOG entry if fixing/changing/adding anything substantial.
• For a new feature or a change in behaviour, I have updated the relevant docstrings in the code to describe the feature or behaviour (please see the doc checklist as well).