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 │ └────────┴─────┴─────┘