Python 极柱内丢失类型信息""

如果我的问题没有多大意义，很抱歉.我对Python 没有太多的经验.

我有一些代码，如下所示:

import polars as pl
from typing import NamedTuple


class Event(NamedTuple):
    name: str
    description: str


def event_table(num) -> list[Event]:
    events = []
    for i in range(5):
        events.append(Event("name", "description"))
    return events


def pretty_string(events: list[Event]) -> str:
    pretty = ""
    for event in events:
        pretty += f"{event.name}: {event.description}\n"
    return pretty

# This does work
print(pretty_string(event_table(5)))

# But then it doesn't work if I have my `list[Event]` in a dataframe
data = {"events": [0, 1, 2, 3, 4]}
df = pl.DataFrame(data).select(events=pl.col("events").map_elements(event_table))

# This doesn't work
pretty_df = df.select(events=pl.col("events").map_elements(pretty_string))
print(pretty_df)

# Neither does this
print(pretty_string(df["events"][0]))

它失败，并出现错误:

Traceback (most recent call last):
  File "path/to/script.py", line 32, in <module>
    pretty_df = df.select(events=pl.col("events").map_elements(pretty_string))
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "path/to/.venv/lib/python3.11/site-packages/polars/dataframe/frame.py", line 8116, in select
    return self.lazy().select(*exprs, **named_exprs).collect(_eager=True)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "path/to/.venv/lib/python3.11/site-packages/polars/lazyframe/frame.py", line 1934, in collect
    return wrap_df(ldf.collect())
                   ^^^^^^^^^^^^^
polars.exceptions.ComputeError: AttributeError: 'dict' object has no attribute 'name'

看来我的list[Event]已经不在df里面了.我不知道该如何让它工作.