---
id: 5e9a093a74c4063ca6f7c15e
title: Data Cleaning with DataFrames
challengeType: 11
videoId: sTMN_pdI6S0
bilibiliIds:
  aid: 505597026
  bvid: BV1Yg411c7bx
  cid: 409018948
dashedName: data-cleaning-with-dataframes
---

# --description--

*Instead of using notebooks.ai like it shows in the video, you can use Google Colab instead.*

More resources:

-  <a href="https://github.com/ine-rmotr-curriculum/data-cleaning-rmotr-freecodecamp" target="_blank" rel="noopener noreferrer nofollow">Notebooks على GitHub</a>
-  <a href="https://colab.research.google.com/github/googlecolab/colabtools/blob/master/notebooks/colab-github-demo.ipynb" target="_blank" rel="noopener noreferrer nofollow">كيفية فتح Notebooks من GitHub باستخدام Google Colab.</a>

# --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--

<pre>
0    1.0
1    1.0
2    2.0
3    3.0
4    3.0
dtype: float64
</pre>

---

<pre>
0    NaN
1    1.0
2    2.0
3    2.0
4    3.0
dtype: float64
</pre>

---

<pre>
0    NaN
1    1.0
2    2.0
3    NaN
4    3.0
dtype: float64
</pre>

## --video-solution--

2