polars.Expr.arg_true

Expr.arg_true() → Expr

Return indices where expression evaluates True.

Warning

Modifies number of rows returned, so will fail in combination with other expressions. Use as only expression in select / with_columns.

See also

Series.arg_true

Return indices where Series is True

polars.arg_where

Examples

>>> df = pl.DataFrame({"a": [1, 1, 2, 1]})
>>> df.select((pl.col("a") == 1).arg_true())
shape: (3, 1)
┌─────┐
│ a   │
│ --- │
│ u32 │
╞═════╡
│ 0   │
│ 1   │
│ 3   │
└─────┘