Add pl.Expr.list.item() as a way to retrieve the single item in a list (or raise when there is none or more than one) #24660
Description
Description
It's a low-priority ask - I came across a problem where it would have been handy.
df_ans = df.with_columns(cs.list().list.item()) # all columns "should" be lists of length 1It takes inspiration from pl.DataFrame.item() which returns the single value unless there is more than one, in which case it raises.
The alternatives are involved - either a cast to an array, an explode, a len() check, or sorting, grabbing the first & last, and asserting equality