id	title	challengeType	videoId	dashedName
5e9a093a74c4063ca6f7c15e	Data Cleaning with DataFrames	11	sTMN_pdI6S0	data-cleaning-with-dataframes

--description--

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

More resources:

--question--

What will the following code print out?

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)

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