Splink 4.0.0: Cannot save completeness chart to PNG

[aalexandersson]

I can no longer save off-line charts to PNG for PDF; I had no problem doing this using Splink 3.9.15. I am using Splink 4.0.0 with the default DuckDB backend on Python 3.11.9 for Windows,

I assume it is a user error (my fault!). It is a new installation of Python and venv. It's a new setup because I encountered dependency hell; for details see discussion issue 2316.

The code below illustrates the issue for the completeness chart. I also cannot save a blocking chart to PNG. I do not have a reprex yet. In the requirements.txt file I have, for example, altair==5.4.0, splink=4.0.0, and vl-convert-python==1.6.0.

from splink.exploratory import completeness_chart  # 
c_completeness = completeness_chart([df1, df2],
    cols=['simulant_id', 
    'first_name', 'last_name', 'ssn', 'sex', 'address', 'city', 
    'state', 'zip', 'street_number', 'street_name', 'dob'],
     db_api=db_api)  
c_completeness.save("c_completeness.png")                   # 

The error message is:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "V:\Testing\Splink_2025\.venv\Lib\site-packages\altair\vegalite\v5\api.py", line 2086, in save
    save(**kwds)
  File "V:\Testing\Splink_2025\.venv\Lib\site-packages\altair\utils\save.py", line 224, in save
    perform_save()
  File "V:\Testing\Splink_2025\.venv\Lib\site-packages\altair\utils\save.py", line 175, in perform_save
    mb_png = spec_to_mimebundle(
             ^^^^^^^^^^^^^^^^^^^
  File "V:\Testing\Splink_2025\.venv\Lib\site-packages\altair\utils\mimebundle.py", line 134, in spec_to_mimebundle
    return _spec_to_mimebundle_with_engine(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "V:\Testing\Splink_2025\.venv\Lib\site-packages\altair\utils\mimebundle.py", line 244, in _spec_to_mimebundle_with_engine
    png = vlc.vegalite_to_png(
          ^^^^^^^^^^^^^^^^^^^^
ValueError: Vega-Lite to PNG conversion failed:
Failed to send SVG conversion request: send failed because receiver is gone

[RobinL]

Does this work?

import altair as alt
df = pd.DataFrame({"x": [2, 3, 4], "y": [5, 5, 3]})
chart = alt.Chart(df).mark_point().encode(x="x", y="y")
chart.save("del.png")

If that fails, the issue is with altair/vl-convert-python as opposed to Splink

[aalexandersson]

The issue was with my RStudio IDE, which I use for automated reporting in PDF. Upgrading RStudio IDE from 2024.04.1+748 (outdated) to 2024.04.2+764 (current) solved the issue.

Robin's code also works; just need to first add import pandas as pd.