polars.col¶
- polars.col(name: Union[str, List[str], List[Type[polars.datatypes.DataType]], polars.internals.series.Series, Type[polars.datatypes.DataType]]) polars.internals.expr.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
- name
A string that holds the name of the column
Examples
>>> df = pl.DataFrame( ... { ... "ham": [1, 2, 3], ... "hamburger": [11, 22, 33], ... "foo": [3, 2, 1], ... } ... ) >>> df.select(pl.col("foo")) shape: (3, 1) ┌─────┐ │ foo │ │ --- │ │ i64 │ ╞═════╡ │ 3 │ ├╌╌╌╌╌┤ │ 2 │ ├╌╌╌╌╌┤ │ 1 │ └─────┘ >>> df.select(pl.col("*")) shape: (3, 3) ┌─────┬───────────┬─────┐ │ ham ┆ hamburger ┆ foo │ │ --- ┆ --- ┆ --- │ │ i64 ┆ i64 ┆ i64 │ ╞═════╪═══════════╪═════╡ │ 1 ┆ 11 ┆ 3 │ ├╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┤ │ 2 ┆ 22 ┆ 2 │ ├╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┤ │ 3 ┆ 33 ┆ 1 │ └─────┴───────────┴─────┘ >>> df.select(pl.col("^ham.*$")) shape: (3, 2) ┌─────┬───────────┐ │ ham ┆ hamburger │ │ --- ┆ --- │ │ i64 ┆ i64 │ ╞═════╪═══════════╡ │ 1 ┆ 11 │ ├╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┤ │ 2 ┆ 22 │ ├╌╌╌╌╌┼╌╌╌╌╌╌╌╌╌╌╌┤ │ 3 ┆ 33 │ └─────┴───────────┘ >>> df.select(pl.col("*").exclude("ham")) shape: (3, 2) ┌───────────┬─────┐ │ hamburger ┆ foo │ │ --- ┆ --- │ │ i64 ┆ i64 │ ╞═══════════╪═════╡ │ 11 ┆ 3 │ ├╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┤ │ 22 ┆ 2 │ ├╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┤ │ 33 ┆ 1 │ └───────────┴─────┘ >>> df.select(pl.col(["hamburger", "foo"])) shape: (3, 2) ┌───────────┬─────┐ │ hamburger ┆ foo │ │ --- ┆ --- │ │ i64 ┆ i64 │ ╞═══════════╪═════╡ │ 11 ┆ 3 │ ├╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┤ │ 22 ┆ 2 │ ├╌╌╌╌╌╌╌╌╌╌╌┼╌╌╌╌╌┤ │ 33 ┆ 1 │ └───────────┴─────┘