`polars col` for expression

Creates a named column expression.

Signature

> polars col {flags} (column name) ...rest

Flags

--type, -t: Treat column names as type names.

Parameters

column name: Name of column to be used. '*' can be used for all columns. Accepts regular expression input; regular expressions should start with ^ and end with $.
...rest: Additional columns to be used. Cannot be '*'.

Input/output types:

input	output
any	polars_expression

Examples

Creates a named column expression and converts it to a nu object

> polars col a | polars into-nu
╭───────┬────────╮
│ expr  │ column │
│ value │ a      │
╰───────┴────────╯

Select all columns using the asterisk wildcard.

> [[a b]; [x 1] [y 2] [z 3]] | polars into-df | polars select (polars col '*') | polars collect
╭───┬───┬───╮
│ # │ a │ b │
├───┼───┼───┤
│ 0 │ x │ 1 │
│ 1 │ y │ 2 │
│ 2 │ z │ 3 │
╰───┴───┴───╯

Select multiple columns (cannot be used with asterisk wildcard)

> [[a b c]; [x 1 1.1] [y 2 2.2] [z 3 3.3]] | polars into-df | polars select (polars col b c | polars sum) | polars collect
╭───┬───┬──────╮
│ # │ b │  c   │
├───┼───┼──────┤
│ 0 │ 6 │ 6.60 │
╰───┴───┴──────╯

Select multiple columns by types (cannot be used with asterisk wildcard)

> [[a b c]; [x o 1.1] [y p 2.2] [z q 3.3]] | polars into-df | polars select (polars col str f64 --type | polars max) | polars collect
╭───┬───┬───┬──────╮
│ # │ a │ b │  c   │
├───┼───┼───┼──────┤
│ 0 │ z │ q │ 3.30 │
╰───┴───┴───┴──────╯

Select columns using a regular expression