polars.count#

polars.count(*columns: str) → Expr[source]#

Return the number of non-null values in the column.

This function is syntactic sugar for col(columns).count().

Calling this function without any arguments returns the number of rows in the context. This way of using the function is deprecated. Please use len() instead.

Parameters:

*columns: One or more column names.

Returns:

Expr: Expression of data type UInt32.

See also

Expr.count

Examples

>>> df = pl.DataFrame(
...     {
...         "a": [1, 2, None],
...         "b": [3, None, None],
...         "c": ["foo", "bar", "foo"],
...     }
... )
>>> df.select(pl.count("a"))
shape: (1, 1)
┌─────┐
│ a   │
│ --- │
│ u32 │
╞═════╡
│ 2   │
└─────┘

Return the number of non-null values in multiple columns.

>>> df.select(pl.count("b", "c"))
shape: (1, 2)
┌─────┬─────┐
│ b   ┆ c   │
│ --- ┆ --- │
│ u32 ┆ u32 │
╞═════╪═════╡
│ 1   ┆ 3   │
└─────┴─────┘

Return the number of rows in a context. This way of using the function is deprecated. Please use len() instead.

>>> df.select(pl.count())  
shape: (1, 1)
┌───────┐
│ count │
│ ---   │
│ u32   │
╞═══════╡
│ 3     │
└───────┘