freeCodeCamp/curriculum/challenges/chinese/08-data-analysis-with-python/data-analysis-with-python-course/data-cleaning-introduction.md

id, challengeType, videoId

id	challengeType	videoId
5e9a093a74c4063ca6f7c15d	11	ovYNhnltVxY

--description--

More resources:

- Notebook

--question--

--text--

What will the following code print out?

import pandas as pd
import numpy as np

s = pd.Series(['a', 3, np.nan, 1, np.nan])

print(s.notnull().sum())

--answers--

3

---

0     True
1     True
2    False
3     True
4    False
dtype: bool

---

0    False
1    False
2     True
3    False
4     True
dtype: bool

--video-solution--

1

--hints--

--solutions--