Wide support for datetime.(date|datetime)

[dangotbanned]

What is your suggestion?

While I was writing #3643 (comment), I was unsatisfied with how a user would need to handle stdlib types.

For example, these two are functionally equivalent:

from datetime import date, datetime

import altair as alt

window_stdlib = (
    datetime(2005, 1, 1).timestamp() * 1e3,
    datetime(2009, 1, 1).timestamp() * 1e3,
)
window_alt = alt.DateTime(year=2005), alt.DateTime(year=2009)

brush = alt.selection_interval(encodings=["x"], value={"x": window_stdlib})
brush = alt.selection_interval(encodings=["x"], value={"x": window_alt})

The need to convert from a format python understands, to one which javascript expects; really seems like a detail that altair should be handling.

Sub Issues

I've opened sub-issues, with this as a parent.

I had already implemented some level of support for these locally, but beyond the shared topic - they touch completely different areas of altair.
For that reason, I'm going to track in smaller individual PRs.

The end goal will be supporting datetime.(date|datetime) in the same way (int|float|bool|str) can be used (schema permitting)

• Support datetime.(date|datetime) as a SchemaBase parameter #3651
• Support datetime.(date|datetime) in Expression(s) #3652

Note

Both original sub-issues are now merged (#3651), (#3652)
Leaving this open in case we discover any blind spots before 5.5.0

Related

• Clarify usage of initial values in selection intervals with dates #3643
  • Inspiration for this new functionality
• Adding datetime.date Support #2199
  • Dealing with a pd.Series[datetime.date] within alt.Chart.data
  • This issue is not focused on this case

[joelostblom]

The need to convert from a format python understands, to one which javascript expects; really seems like a detail that altair should be handling.

I totally agree, thanks for working on this @dangotbanned!