Save multiple charts with same selenium instance

One of the benefits that lead me to altair was the ability to generate vega-lite json that can be used in the to generate and save charts locally and in the browser. I’ve been able to save via the browser and locally.

Viewing and saving in the browser is nice for single charts. Saving locally is nice for saving a lot of charts programically (~50 charts). When saving locally altiar launches a selenium instance and a session to render and save the chart. This can be a little slow.

To reuse the selenium resources as much as possible, is there a way I can save multiple charts at once? Something like this would satisfy my desire for a small speed increase:

alt.save(*chart_list)

[jakevdp]

This is now implemented automatically in http://github.com/altair-viz/altair_saver. I plan to remove all selenium-based code from Altair itself, and require installation of altiar_saver for programmatic saving of PNG, SVG, and PDF.

[ehudkr]

Apologies for waking up this thread, but since no solution was implemented in altair yet (as far as I can tell), I would like to point out that there’s a good opportunity to get two scoops in one cone here. I propose allowing Chart.save() to receive an initialized selenium webdriver instance instead of a string. This way one can reuse the same webdriver over multiple saves, avoiding the overhead of save() initializing a new one each time:

from selenium import webdriver
driver = webdriver.Chrome()
# Generate altair charts...
for i, chart in enumerate(chart_list):
    chart.save(f"chart_{i}", webdriver=driver)

I think this might be a cleaner solution (API-wise) from altair’s point of view, as it avoids complicated user inputs, such as specifying lists/tuples of charts, file-names, and keyword-arguments.

As for the two-for-one: The other benefit of such a solution is that it also solves https://github.com/altair-viz/altair/issues/1619 and allows users greater freedom in how they set their work environment (for example, working on remote machines where one may not have permissions to PATH or /bin in order to point to webdriver executables. Users can specify arbitrary locations when initializing the driver: webdriver.Chrome('path/to/webdriver.exe)).