polars.arg_where

polars.arg_where(
    condition: Expr | Series,
    *,
    eager: bool = False,
) → Expr | Series

Return indices where condition evaluates True.

Parameters:

condition

Boolean expression to evaluate

eager

Evaluate immediately and return a Series; this requires that the given condition is itself a Series. If set to False (default), return an expression instead.

See also

Series.arg_true

Return indices where Series is True

Examples

>>> df = pl.DataFrame({"a": [1, 2, 3, 4, 5]})
>>> df.select(
...     [
...         pl.arg_where(pl.col("a") % 2 == 0),
...     ]
... ).to_series()
shape: (2,)
Series: 'a' [u32]
[
    1
    3
]