Output widget custom export

[casperdcl]

Trying to make an output context widget exportable to pain-text. Overriding __repr__ doesn't work. Simple example:

# In [1]:
from ipywidgets import Output
from IPython import display as disp

class MyOutput(Output):
    def __init__(self):
        super(Output, self).__init__()
        self.last_display = "Nothing to display yet"
    def __repr__(self):
        return repr(self.last_display)

out1 = MyOutput()
disp.display(out1)  # display in `Out[1]`

# In [2]:
with out1:  # use `Out[1]`
    disp.clear_output(True)
    disp.display("Some text!")

This correctly displays 'Some text!' in Out[1], but when exported shows 'Nothing to display yet'. If __repr__ is not overridden, exported versions just show Output().

Any idea how to create an Output context with manually controlled export repr? Should we be using _repr_mimebundle_ from https://ipython.readthedocs.io/en/stable/api/generated/IPython.display.html#IPython.display.display or https://ipypublish.readthedocs.io/en/latest/code_cells.html#object-output-formats ? Seems extreme and also doesn't seem to work for an Output context widget.

• related: Converting widgets to static png #2280
• original post: TQDM progress bars in jupyter notebooks do not appear in PDF via latex output  tqdm/tqdm#937
• follow-up summary: Saved ASCII output from tqdm.notebook shows zero progress tqdm/tqdm#1120 (comment)