polars.lazyframe.group_by.LazyGroupBy.count

LazyGroupBy.count() → LazyFrame

Count the number of values in each group.

Warning

null is deemed a value in this context.

Examples

>>> ldf = pl.DataFrame(
...     {
...         "a": [1, 2, 2, 3, 4, 5],
...         "b": [0.5, 0.5, 4, 10, 13, 14],
...         "c": [True, True, True, False, False, True],
...         "d": ["Apple", "Orange", "Apple", "Apple", "Banana", "Banana"],
...     }
... ).lazy()
>>> ldf.group_by("d", maintain_order=True).count().collect()
shape: (3, 2)
┌────────┬───────┐
│ d      ┆ count │
│ ---    ┆ ---   │
│ str    ┆ u32   │
╞════════╪═══════╡
│ Apple  ┆ 3     │
│ Orange ┆ 1     │
│ Banana ┆ 2     │
└────────┴───────┘