Pandas: Replace all the NaN values with Zero's in a column of a dataframe

Last update on May 01 2025 12:54:42 (UTC/GMT +8 hours)

32. Replace NaN with Zeros

Write a Pandas program to replace all the NaN values with Zero's in a column of a dataframe.

Sample data:
Original DataFrame
attempts name qualify score
0 1 Anastasia yes 12.5
1 3 Dima no 9.0
2 2 Katherine yes 16.5
3 3 James no NaN
4 2 Emily no 9.0
5 3 Michael yes 20.0
6 1 Matthew yes 14.5
7 1 Laura no NaN
8 2 Kevin no 8.0
9 1 Jonas yes 19.0
New DataFrame replacing all NaN with 0:
attempts name qualify score
0 1 Anastasia yes 12.5
1 3 Dima no 9.0
2 2 Katherine yes 16.5
3 3 James no 0.0
4 2 Emily no 9.0
5 3 Michael yes 20.0
6 1 Matthew yes 14.5
7 1 Laura no 0.0
8 2 Kevin no 8.0
9 1 Jonas yes 19.0

Sample Solution :

Python Code :

import pandas as pd
import numpy as np
exam_data = {'name': ['Anastasia', 'Dima', 'Katherine', 'James', 'Emily', 'Michael', 'Matthew', 'Laura', 'Kevin', 'Jonas'],
        'score': [12.5, 9, 16.5, np.nan, 9, 20, 14.5, np.nan, 8, 19],
        'attempts': [1, 3, 2, 3, 2, 3, 1, 1, 2, 1],
        'qualify': ['yes', 'no', 'yes', 'no', 'no', 'yes', 'yes', 'no', 'no', 'yes']}
df = pd.DataFrame(exam_data)
print("Original DataFrame")
print(df)
df =  df.fillna(0)
print("\nNew DataFrame replacing all NaN with 0:")
print(df)

Sample Output:

 Original DataFrame
   attempts       name qualify  score
0         1  Anastasia     yes   12.5
1         3       Dima      no    9.0
2         2  Katherine     yes   16.5
3         3      James      no    NaN
4         2      Emily      no    9.0
5         3    Michael     yes   20.0
6         1    Matthew     yes   14.5
7         1      Laura      no    NaN
8         2      Kevin      no    8.0
9         1      Jonas     yes   19.0

New DataFrame replacing all NaN with 0:
   attempts       name qualify  score
0         1  Anastasia     yes   12.5
1         3       Dima      no    9.0
2         2  Katherine     yes   16.5
3         3      James      no    0.0
4         2      Emily      no    9.0
5         3    Michael     yes   20.0
6         1    Matthew     yes   14.5
7         1      Laura      no    0.0
8         2      Kevin      no    8.0
9         1      Jonas     yes   19.0

Explanation:

The above code creates a Pandas DataFrame called ‘df’ from a dictionary called ‘exam_data’ that contains information about students and their exam scores. Some of the students have missing scores, which are represented as np.nan values.

df = df.fillna(0): The fillna() method is then used to fill in these missing values with 0.

Finally the resulting DataFrame is printed to the console using print() function.

For more Practice: Solve these Related Problems:

Write a Pandas program to replace NaN values with zeros in a specified column and then check data types remain unchanged.
Write a Pandas program to fill NaN values with zero across multiple columns using the fillna() method.
Write a Pandas program to update a DataFrame column by replacing all NaN entries with zero and then plot a histogram of the column.
Write a Pandas program to conditionally replace NaN values with zero only if the column's mean is below a threshold.

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Python-Pandas Code Editor:

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