Python Polars表达式无法访问中间列创建表达式

我想用整数编码这non-zero个二进制事件.下面是一个演示表:

import polars as pl
df = pl.DataFrame(
    {
        "event": [0, 1, 1, 0],
        "foo": [1, 2, 3, 4],
        "boo": [2, 3, 4, 5],
    }
)

预期yields 通过以下方式实现:

df = df.with_row_index()
events = df.select(pl.col(["index", "event"])).filter(pl.col("event") == 1).with_row_index("event_id").drop("event")
df = df.join(events, on="index", how="left")

out:
shape: (4, 5)
┌───────┬───────┬─────┬─────┬──────────┐
│ index ┆ event ┆ foo ┆ boo ┆ event_id │
│ ---   ┆ ---   ┆ --- ┆ --- ┆ ---      │
│ u32   ┆ i64   ┆ i64 ┆ i64 ┆ u32      │
╞═══════╪═══════╪═════╪═════╪══════════╡
│ 0     ┆ 0     ┆ 1   ┆ 2   ┆ null     │
│ 1     ┆ 1     ┆ 2   ┆ 3   ┆ 0        │
│ 2     ┆ 1     ┆ 3   ┆ 4   ┆ 1        │
│ 3     ┆ 0     ┆ 4   ┆ 5   ┆ null     │
└───────┴───────┴─────┴─────┴──────────┘

我希望得到chaining the expressions的预期输出:

(
    df
    .with_row_index()
    .join(
        df
        .select(pl.col(["index", "event"]))
        .filter(pl.col("event") == 1)
        .with_row_index("event_id")
        .drop("event"),
        on="index",
        how="left",
        )
    )

但是，.join()表达式中的表达式似乎没有添加df.with_row_index()运算中的index列:

ColumnNotFoundError: index

Error originated just after this operation:
DF ["event", "foo", "boo"]; PROJECT */3 COLUMNS; SELECTION: "None"