Name and location of json files created by `alt.data_transformers.enable('json')`

Hello, First, I love this package that I discovered recently and was able to get up to speed really quickly with the tutorials, so thank you!

I use alt.data_transformers.enable('json') to manage fairly large datasets, but when I make several graphs in a notebook, I get a bunch of altair-data-11217bb8-d26d-481e-99d3-8e8701d4e6cf.json-like files, and it is not easy to know which one is which. Is there a way to:

1. Select a location (e.g. a figure file containing those files) ?
2. Choose a name when rendering the file (maybe with the name of the Chart if provided) ?

Thank you

[jakevdp]

You can always find the filename in the serialized chart:

import altair as alt
import pandas as pd
df = pd.DataFrame({'x': range(5)})

alt.data_transformers.enable('json')
chart = alt.Chart(df).mark_bar().encode(x='x:Q')

print(chart.to_dict()['data']['url'])

Better would probably be to do the transformation manually if you want to manipulate the output file directly:

data = alt.to_json(df)
print(data['url'])
chart = alt.Chart(data).mark_bar().encode(x='x:Q')

[jakevdp]

I’m not sure that would work, because the dataset is not known at the time that the transformer is enabled.