# ds1000 / 91

- taskset: [ds1000](https://harnessreport.com/tasks/ds1000.md)
- difficulty: 
- category: 
- language: 
- runnable from the site: no
- agent timeout: 1800s

## Results by harness

_none yet_

## Instruction

```
# 91: DS-1000 Task

## Prompt
Problem:
I have multi-index df as follows


                x  y
id  date            
abc 3/1/1994  100  7
    9/1/1994   90  8
    3/1/1995   80  9
Where dates are stored as str.


I want to parse date index. The following statement


df.index.levels[1] = pd.to_datetime(df.index.levels[1])
returns error:


TypeError: 'FrozenList' does not support mutable operations.


A:
<code>
import pandas as pd


index = pd.MultiIndex.from_tuples([('abc', '3/1/1994'), ('abc', '9/1/1994'), ('abc', '3/1/1995')],
                                 names=('id', 'date'))
df = pd.DataFrame({'x': [100, 90, 80], 'y':[7, 8, 9]}, index=index)
</code>
df = ... # put solution in this variable
BEGIN SOLUTION
<code>

## What to do
- Edit `solution/solution.py` so the code passes the DS-1000 tests.
- Do not access the internet or install new packages; required libraries are preinstalled in the Docker image.
- Run tests locally via `bash tests/test.sh`.

## Notes
- Keep the variable names/signatures implied by the prompt/code_context.
- The evaluator uses the original DS-1000 `code_context` (`test_execution` / `test_string`).
```
---
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