df.fillna(0) code example

Example 1: fillna with mean pandas

sub2['income'].fillna((sub2['income'].mean()), inplace=True)

Example 2: python pandas fillna

# importing pandas module
import pandas as pd  
# making data frame from csv file
nba = pd.read_csv("nba.csv")
  
# replacing na values in college with No college
nba["College"].fillna("No College", inplace = True)
# OR
nba.College.fillna("No College", inplace = True)
  
print(nba)

Example 3: replace nan using fillna

>>> df.fillna(0)
    A   B   C   D
0   0.0 2.0 0.0 0
1   3.0 4.0 0.0 1
2   0.0 0.0 0.0 5
3   0.0 3.0 0.0 4

Example 4: replace nan using fillna

>>> df.fillna(method='ffill')
    A   B   C   D
0   NaN 2.0 NaN 0
1   3.0 4.0 NaN 1
2   3.0 4.0 NaN 5
3   3.0 3.0 NaN 4