Last second line What is value used for ? how does computer were to fill in that value?

Installations & Python Packages
1

import pandas as pd

d = {

       'AAPL' : pd.Series([10, 20, 30],     index=['P1', 'P2', 'P3']),

       'GOOGL' : pd.Series([44, 50, 75, 89], index=['P1', 'P2', 'P3', 'P4'])

    }

df = pd.DataFrame(d)

Type your code below

print (df)

df_mod = df.fillna(value='10')

print (df_mod)

2

When you print dataframe df, you will observe there is a NaN value at (P4, AAPL). fillna() method fills that NaN value with the specified value that is 10, in this case.