Pandas: Update null elements with value in the same location in other

Last update on May 02 2025 12:49:42 (UTC/GMT +8 hours)

15. Combine DataFrames by Filling Nulls from Another

Write a Pandas program to Combine two DataFrame objects by filling null values in one DataFrame with non-null values from other DataFrame.

Test Data:

Original DataFrames:
     A  B
0  NaN  3
1  0.0  4
2  NaN  5

Sample Solution:

Python Code :

import pandas as pd
df1 = pd.DataFrame({'A': [None, 0, None], 'B': [3, 4, 5]})
df2 = pd.DataFrame({'A': [1, 1, 3], 'B': [3, None, 3]})
df1.combine_first(df2)
print("Original DataFrames:")
print(df1)
print("--------------------")
print(df2)
print("\nMerge two dataframes with different columns:")
result = df1.combine_first(df2)
print(result)

Sample Output:

Original DataFrames:
     A  B
0  NaN  3
1  0.0  4
2  NaN  5
--------------------
   A    B
0  1  3.0
1  1  NaN
2  3  3.0

Merge two dataframes with different columns:
     A  B
0  1.0  3
1  0.0  4
2  3.0  5

For more Practice: Solve these Related Problems:

Write a Pandas program to combine two DataFrames by filling null values in one with non-null values from the other using combine_first().
Write a Pandas program to merge two DataFrames and then use fillna() to replace missing entries from one DataFrame with values from the other.
Write a Pandas program to update a DataFrame by filling its null values with corresponding non-null values from a second DataFrame and then output the result.
Write a Pandas program to combine two DataFrames with overlapping data by filling missing data from one DataFrame with available data from the other.

Go to:

Previous: Write a Pandas program to merge two given dataframes with different columns.

Python Code Editor:

Have another way to solve this solution? Contribute your code (and comments) through Disqus.