Differing behaviors between classic Jupyter Notebook and JupyterLab for ipywidgets

I recently inherited some code from someone and in the process of trying to run it in a classic Jupyter Notebook and in JupyterLab (and VS Code), I noticed it behaves slightly different in each. Below is stripped down minimal code to reproduce the behavior I’m seeing, and I’ve preserved the structure of the code (my disclaimer that it’s a bit odd and not optimal) in case that comes into play.

In a classic Jupyter Notebook, when either the button is clicked or the dropdown changes new output is produced and sent to the output of the cell. But in JupyterLab the output is sent to the Log and the output in the cell stays the same. Interestingly VS Code has similar behavior as JupyterLab in that the output stays the same and warnings/info messages are thrown. I know you can’t speak to VS Code, but I thought I’d mention it in case it helps. Also if it helps, in VS Code, in the Output - Jupyter section it gives the following warnings/info messages when the dropdown widget is changed:

Info 2021-07-19 10:36:07: Unhandled widget kernel message: display_data [object Object]
Unhandled kernel message from a widget: display_data : {"data":{"text/plain":"<Figure size 432x288 with 1 Axes>","image/png":"iVBORw0KGgoAAAANSUhEUg [truncated]

and the following when the button is clicked:

Info 2021-07-19 10:38:18: Unhandled widget kernel message: stream [object Object]
Unhandled kernel message from a widget: stream : {"name":"stdout","text":"X4\n"}

My hunch is that this isn’t a bug per-se but that, but rather that the code improperly relies on behavior that differs between a classic Jupyter Notebook and JupyterLab (and VS Code). Any ideas as to what the issue may be or what the differing behaviors are and why it works in a classic Jupyter Notebook but not JupyterLab?


Setup versioning:
Python 3.6.12 |Anaconda, Inc.| (default, Sep 8 2020, 17:50:39)
notebook 6.4.0
jupyterlab 3.0.16
ipywidgets 7.6.3
IPython 7.16.1
matplotlib 3.3.4
seaborn 0.11.1

Firefox 90.0.1

macOS Big Sur (11.4)

In testing I was able to reproduce the behavior in the classic Jupyter Notebook by launching the classic notebook from JupyterLab.

I’m also posting this on the VS Code - Jupyter Extension and ipywidgets forums/github.

import ipywidgets
import IPython

import numpy as np
import pandas as pd

import seaborn as sns

df_1 = pd.DataFrame(np.random.randint(1, 5, (10, 5))).add_prefix("X")

def getHist(df, var_name):
    import matplotlib.pyplot as plt
    table = df
    fig, ax = plt.subplots()

class UI():
    def __init__(self):
        self._select_widget = ipywidgets.Dropdown(options = df_1.columns.tolist())
        self._select_widget.observe(self._on_value_change, names = "value")
        self._print_Data_syntax_button = ipywidgets.Button(description = "Data Syntax")
        self._vbox = ipywidgets.VBox([self._print_Data_syntax_button,
    def _on_value_change(self, change):
    def _displayUI(self):
    def _display(self):
        getHist(df_1, self._select_widget.value)
    def _on_button_clicked_print_Data_syntax(self, change):

ui1 = UI()