polars.count#

polars.count(column: str) Expr[source]#
polars.count(column: Series) int
polars.count(column: None = None) Expr

Count the number of values in this column/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.groupby("c", maintain_order=True).agg(pl.count())
shape: (2, 2)
┌─────┬───────┐
│ c   ┆ count │
│ --- ┆ ---   │
│ str ┆ u32   │
╞═════╪═══════╡
│ foo ┆ 2     │
├╌╌╌╌╌┼╌╌╌╌╌╌╌┤
│ bar ┆ 1     │
└─────┴───────┘