polars.count

polars.count(column: str) → Expr

polars.count(column: Series) → int

polars.count(column: None = None) → Expr

Count the number of values in this column/context.

Warning

null is deemed a value in this context.

Parameters:

column

If dtype is:

• pl.Series : count the values in the Series.

• str : count the values in this column.

• None : count the number of values in this context.

Examples

>>> df = pl.DataFrame({"a": [1, 8, 3], "b": [4, 5, 2], "c": ["foo", "bar", "foo"]})
>>> df.select(pl.count())
shape: (1, 1)
┌───────┐
│ count │
│ ---   │
│ u32   │
╞═══════╡
│ 3     │
└───────┘
>>> df.group_by("c", maintain_order=True).agg(pl.count())
shape: (2, 2)
┌─────┬───────┐
│ c   ┆ count │
│ --- ┆ ---   │
│ str ┆ u32   │
╞═════╪═══════╡
│ foo ┆ 2     │
│ bar ┆ 1     │
└─────┴───────┘