Function col

  • col(col: string | DataType | string[] | pl.Series<any, string>): pl.Expr

    A column in a DataFrame. Can be used to select:

    • a single column by name
    • all columns by using a wildcard "*"
    • column by regular expression if the regex starts with ^ and ends with $

    Parameters

    Returns pl.Expr

    Example

    > df = pl.DataFrame({
    > "ham": [1, 2, 3],
    > "hamburger": [11, 22, 33],
    > "foo": [3, 2, 1]})
    > df.select(col("foo"))
    shape: (3, 1)
    ╭─────╮
    │ foo │
    │ --- │
    │ i64 │
    ╞═════╡
    │ 3   │
    ├╌╌╌╌╌┤
    │ 2   │
    ├╌╌╌╌╌┤
    │ 1   │
    ╰─────╯
    > df.select(col("*"))
    shape: (3, 3)
    ╭─────┬───────────┬─────╮
    │ ham ┆ hamburger ┆ foo │
    │ --- ┆ ---       ┆ --- │
    │ i64 ┆ i64       ┆ i64 │
    ╞═════╪═══════════╪═════╡
    │ 1   ┆ 11        ┆ 3   │
    ├╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┤
    │ 2   ┆ 22        ┆ 2   │
    ├╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┤
    │ 3   ┆ 33        ┆ 1   │
    ╰─────┴───────────┴─────╯
    > df.select(col("^ham.*$"))
    shape: (3, 2)
    ╭─────┬───────────╮
    │ ham ┆ hamburger │
    │ --- ┆ ---       │
    │ i64 ┆ i64       │
    ╞═════╪═══════════╡
    │ 1   ┆ 11        │
    ├╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┤
    │ 2   ┆ 22        │
    ├╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┤
    │ 3   ┆ 33        │
    ╰─────┴───────────╯
    > df.select(col("*").exclude("ham"))
    shape: (3, 2)
    ╭───────────┬─────╮
    │ hamburger ┆ foo │
    │ ---       ┆ --- │
    │ i64       ┆ i64 │
    ╞═══════════╪═════╡
    │ 11        ┆ 3   │
    ├╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┤
    │ 22        ┆ 2   │
    ├╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┤
    │ 33        ┆ 1   │
    ╰───────────┴─────╯
    > df.select(col(["hamburger", "foo"])
    shape: (3, 2)
    ╭───────────┬─────╮
    │ hamburger ┆ foo │
    │ ---       ┆ --- │
    │ i64       ┆ i64 │
    ╞═══════════╪═════╡
    │ 11        ┆ 3   │
    ├╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┤
    │ 22        ┆ 2   │
    ├╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┤
    │ 33        ┆ 1   │
    ╰───────────┴─────╯
    > df.select(col(pl.Series(["hamburger", "foo"]))
    shape: (3, 2)
    ╭───────────┬─────╮
    │ hamburger ┆ foo │
    │ ---       ┆ --- │
    │ i64       ┆ i64 │
    ╞═══════════╪═════╡
    │ 11        ┆ 3   │
    ├╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┤
    │ 22        ┆ 2   │
    ├╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┤
    │ 33        ┆ 1   │
    ╰───────────┴─────╯

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