How to select the last non-null value from one column and also the value from another column on the same row in Polars?

Below is a non working example in which I retrieve the last available ‘Open’ but how do I get corresponding ‘Time’?

sel = self.data.select([pl.col('Time'),
    pl.col('Open').drop_nulls().last()])

>Solution :

For instance, you can use .filter() to select rows that do not contain null and then take last row

Here example:

df = pl.DataFrame({
    "a": [1,2,3,4,5],
    "b": ["cat", None, "owl", None, None]
})

┌─────┬──────┐
│ a   ┆ b    │
│ --- ┆ ---  │
│ i64 ┆ str  │
╞═════╪══════╡
│ 1   ┆ cat  │
│ 2   ┆ null │
│ 3   ┆ owl  │
│ 4   ┆ null │
│ 5   ┆ null │
└─────┴──────┘

df.filter(
    pl.col("b").is_not_null()
).select(pl.all().last())

┌─────┬─────┐
│ a   ┆ b   │
│ --- ┆ --- │
│ i64 ┆ str │
╞═════╪═════╡
│ 3   ┆ owl │
└─────┴─────┘