issues: 1125297737

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id node_id number title user state locked assignee milestone comments created_at updated_at closed_at author_association pull_request body repo type active_lock_reason performed_via_github_app reactions draft state_reason
1125297737 I_kwDOCGYnMM5DEq5J 402 Advanced class-based `conversions=` mechanism 9599 open 0     14 2022-02-06T19:47:41Z 2022-02-16T10:18:55Z   OWNER  

The conversions= parameter works like this at the moment: https://sqlite-utils.datasette.io/en/3.23/python-api.html#converting-column-values-using-sql-functions

python db["places"].insert( {"name": "Wales", "geometry": wkt}, conversions={"geometry": "GeomFromText(?, 4326)"}, ) This proposal is to support values in that dictionary that are objects, not strings, which can represent more complex conversions - spun out from #399.

New proposed mechanism: ```python from sqlite_utils.utils import LongitudeLatitude

db["places"].insert( { "name": "London", "point": (-0.118092, 51.509865) }, conversions={"point": LongitudeLatitude}, ) `` HereLongitudeLatitudeis a magical value which does TWO things: it sets up theGeomFromText(?, 4326)SQL function, and it handles converting the(51.509865, -0.118092)tuple into aPOINT({} {})` string.

This would involve a change to the conversions= contract - where it usually expects a SQL string fragment, but it can also take an object which combines that SQL string fragment with a Python conversion function.

Best of all... this resolves the lat, lon v.s. lon, lat dilemma because you can use from sqlite_utils.utils import LongitudeLatitude OR from sqlite_utils.utils import LatitudeLongitude depending on which you prefer!

Originally posted by @simonw in https://github.com/simonw/sqlite-utils/issues/399#issuecomment-1030739566

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