polars.first#
- polars.first(*columns: str) Expr [source]#
Get the first value.
This function has different behavior depending on the input type:
None
-> Takes first column of a context (equivalent tocs.first()
).str
or[str,]
-> Syntactic sugar forpl.col(columns).first()
.
- Parameters:
- *columns
One or more column names. If not provided (default), returns an expression to take the first column of the context instead.
Examples
>>> df = pl.DataFrame( ... { ... "a": [1, 8, 3], ... "b": [4, 5, 2], ... "c": ["foo", "bar", "baz"], ... } ... ) >>> df.select(pl.first()) shape: (3, 1) ┌─────┐ │ a │ │ --- │ │ i64 │ ╞═════╡ │ 1 │ │ 8 │ │ 3 │ └─────┘ >>> df.select(pl.first("b")) shape: (1, 1) ┌─────┐ │ b │ │ --- │ │ i64 │ ╞═════╡ │ 4 │ └─────┘ >>> df.select(pl.first("a", "c")) shape: (1, 2) ┌─────┬─────┐ │ a ┆ c │ │ --- ┆ --- │ │ i64 ┆ str │ ╞═════╪═════╡ │ 1 ┆ foo │ └─────┴─────┘