---
id: 5e9a093a74c4063ca6f7c15e
title: Data Cleaning with DataFrames
challengeType: 11
isHidden: false
videoId: sTMN_pdI6S0
---
## Description
## Tests
````yml
question:
text: |
What will the following code print out?
```py
import pandas as pd
import numpy as np
s = pd.Series([np.nan, 1, 2, np.nan, 3])
s = s.fillna(method='ffill')
print(s)
```
answers:
- |
```
0 1.0
1 1.0
2 2.0
3 3.0
4 3.0
dtype: float64
```
- |
```
0 NaN
1 1.0
2 2.0
3 2.0
4 3.0
dtype: float64
```
- |
```
0 NaN
1 1.0
2 2.0
3 NaN
4 3.0
dtype: float64
```
solution: 2
````