saving png with chart.save() is not enabled with vl-convert-python

[HorvathAP]

I'm trying to save a chart as png on Google Colab.
altair.version==5.0.0
vl-convert-python.version==1.0.1

The documentation would suggest that I can use chart.save('chart.png') so long as vl-convert-python is installed, but I'm still getting this error:

"ValueError: Saving charts in 'png' format requires the altair_saver package"

I've also tried altair_saver, but got a wide variety of errors and I ultimately found this issue which concluded that vl-convert was recommended: altair-viz/altair_saver#121

[binste]

You're right that it should be enough to have vl-convert-python installed and then call chart.save("chart.png"). Can you provide a link to a minimal Colab notebook which shows this issue? Without it, it's difficult to know what's going on.

[jonmmease]

Hi @HorvathAP,

Could you try checking the versions from Python.

import vl_convert as vlc
print(vlc.__version__)

And for Altair

import altair as alt
print(alt.__version__)

I ask because the error message looks like it's coming from Altair 4. Did you have to install Altair 5 manually with !pip install, or does Colab ship with Altair 5?

[HorvathAP]

Yes, I was installing altair 5 with !pip install altair==5.0.0 But it looks like I wasn't paying close enough attention to restarting my runtime with each pip install. Verifying the version reminded me that a runtime restart is necessary. chart.save() is working with a proper install of altair 5. Thanks, and sorry for the confusion.

[binste]

No worries! Glad it works :)