polars.Expr.inspect

Expr.inspect(fmt: str = '{}') → Self

Print the value that this expression evaluates to and pass on the value.

Examples

>>> df = pl.DataFrame({"foo": [1, 1, 2]})
>>> df.select(pl.col("foo").cum_sum().inspect("value is: {}").alias("bar"))
value is: shape: (3,)
Series: 'foo' [i64]
[
    1
    2
    4
]
shape: (3, 1)
┌─────┐
│ bar │
│ --- │
│ i64 │
╞═════╡
│ 1   │
│ 2   │
│ 4   │
└─────┘