Pandas: Replace NaNs with a single constant value

Last update on May 02 2025 12:50:51 (UTC/GMT +8 hours)

12. Replace NaNs with a Constant in Specified Columns

Write a Pandas program to replace NaNs with a single constant value in specified columns in a DataFrame.

Test Data:

     ord_no  purch_amt    ord_date  customer_id
0       NaN        NaN         NaN          NaN
1       NaN     270.65  2012-09-10       3001.0
2   70002.0      65.26         NaN       3001.0
3       NaN        NaN         NaN          NaN
4       NaN     948.50  2012-09-10       3002.0
5   70005.0    2400.60  2012-07-27       3001.0
6       NaN    5760.00  2012-09-10       3001.0
7   70010.0    1983.43  2012-10-10       3004.0
8   70003.0    2480.40  2012-10-10       3003.0
9   70012.0     250.45  2012-06-27       3002.0
10      NaN      75.29  2012-08-17       3001.0
11      NaN        NaN         NaN          NaN

Sample Solution:

Python Code :

import pandas as pd
import numpy as np
pd.set_option('display.max_rows', None)
#pd.set_option('display.max_columns', None)
df = pd.DataFrame({
'ord_no':[70001,np.nan,70002,70004,np.nan,70005,np.nan,70010,70003,70012,np.nan,70013],
'purch_amt':[150.5,270.65,65.26,110.5,948.5,2400.6,5760,1983.43,2480.4,250.45, 75.29,3045.6],
'ord_date': ['2012-10-05','2012-09-10',np.nan,'2012-08-17','2012-09-10','2012-07-27','2012-09-10','2012-10-10','2012-10-10','2012-06-27','2012-08-17','2012-04-25'],
'customer_id':[3002,3001,3001,3003,3002,3001,3001,3004,3003,3002,3001,3001],
'salesman_id':[5002,5003,5001,np.nan,5002,5001,5001,np.nan,5003,5002,5003,np.nan]})
print("Original Orders DataFrame:")
print(df)
print("\nReplace NaNs with a single constant value:")
result = df['ord_no'].fillna(0, inplace=False)
print(result)

Sample Output:

Original Orders DataFrame:
     ord_no  purch_amt    ord_date  customer_id  salesman_id
0   70001.0     150.50  2012-10-05         3002       5002.0
1       NaN     270.65  2012-09-10         3001       5003.0
2   70002.0      65.26         NaN         3001       5001.0
3   70004.0     110.50  2012-08-17         3003          NaN
4       NaN     948.50  2012-09-10         3002       5002.0
5   70005.0    2400.60  2012-07-27         3001       5001.0
6       NaN    5760.00  2012-09-10         3001       5001.0
7   70010.0    1983.43  2012-10-10         3004          NaN
8   70003.0    2480.40  2012-10-10         3003       5003.0
9   70012.0     250.45  2012-06-27         3002       5002.0
10      NaN      75.29  2012-08-17         3001       5003.0
11  70013.0    3045.60  2012-04-25         3001          NaN

Replace NaNs with a single constant value:
0     70001.0
1         0.0
2     70002.0
3     70004.0
4         0.0
5     70005.0
6         0.0
7     70010.0
8     70003.0
9     70012.0
10        0.0
11    70013.0
Name: ord_no, dtype: float64

For more Practice: Solve these Related Problems:

Write a Pandas program to substitute missing values in selected columns with a given constant value.
Write a Pandas program to replace NaN entries in specific DataFrame columns with a fixed number or string.
Write a Pandas program to use the fillna() function to set a constant value for NaNs in a subset of columns.
Write a Pandas program to update only designated columns by replacing all NaN values with a predefined constant.

Go to:

Previous: Write a Pandas program to calculate the total number of missing values in a DataFrame.
Next: Write a Pandas program to replace NaNs with the value from the previous row or the next row in a given DataFrame.

Python Code Editor:

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