polars.LazyFrame.with_row_count¶

LazyFrame.with_row_count(name: str = 'row_nr', offset: int = 0) → polars.internals.lazy_frame.LDF¶

Add a column at index 0 that counts the rows.

..warning::: This can have a negative effect on query performance. This may for instance block predicate pushdown optimization.

Parameters

name: Name of the column to add.
offset: Start the row count at this offset

Examples

>>> df = pl.DataFrame(
...     {
...         "a": [1, 3, 5],
...         "b": [2, 4, 6],
...     }
... ).lazy()
>>> df.with_row_count().collect()
shape: (3, 3)
┌────────┬─────┬─────┐
│ row_nr ┆ a   ┆ b   │
│ ---    ┆ --- ┆ --- │
│ u32    ┆ i64 ┆ i64 │
╞════════╪═════╪═════╡
│ 0      ┆ 1   ┆ 2   │
├╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌┤
│ 1      ┆ 3   ┆ 4   │
├╌╌╌╌╌╌╌╌┼╌╌╌╌╌┼╌╌╌╌╌┤
│ 2      ┆ 5   ┆ 6   │
└────────┴─────┴─────┘

polars.LazyFrame.show_graph polars.LazyFrame.inspect