Pass as immutable values, and try to enforce schema (eg, arrow) to keep typed & predictable. This is generally easy by ensuring initial data loads get validated, and then basic testing of subsequent operations goes far.

If python had dependent types, that's how i'd think about them, and keeping them typed would be even easier, eg, nulls sneaking in unexpectedly and breaking numeric columns

When using something like dask, which forces stronger adherence to typings, this can get more painful