`Cell.first_not_none`

[lars-reimann]

Is your feature request related to a problem?

When transforming a column of a table or computing a new one, it is sometimes beneficial to compute multiple values and pick the first that is not None. For example, we might try to transform a column that contains date strings in various formats into an actual date column.

Desired solution

Add a static method Cell.first_not_none. It should have one parameter cells: list[Cell] and return a new cell containing the first non-None cell value. The implementation should use the _LazyCell.

Use pl.coalesce internally.

Return None if all conversions returned None.

Possible alternatives (optional)

No response

Screenshots (optional)

No response

Additional Context (optional)

No response

[LIEeOoNn]

we tried for 2h to implement it but apparently can't be wrapped by polars and stopped after trying everything we could think :(

[lars-reimann]

Do you have your current code in some branch?

[LIEeOoNn]

Do you have your current code in some branch?

we do at #799

[lars-reimann]

I've pushed an implementation of first_not_none to 799-cellfirst_not_none. It still needs documentation (including example usage) and tests, though.