Pandas: Merge two dataframes with different columns

Last update on May 02 2025 12:49:41 (UTC/GMT +8 hours)

14. Merge DataFrames with Different Columns

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

Test Data:

data1:
  key1 key2   P   Q
0   K0   K0  P0  Q0
1   K0   K1  P1  Q1
2   K1   K0  P2  Q2
3   K2   K1  P3  Q3

data2:
  key1 key2   R   S
0   K0   K0  R0  S0
1   K1   K0  R1  S1
2   K1   K0  R2  S2
3   K2   K0  R3  S3

Sample Solution:

Python Code :

import pandas as pd
data1 = pd.DataFrame({'key1': ['K0', 'K0', 'K1', 'K2'],
                     'key2': ['K0', 'K1', 'K0', 'K1'],
                     'P': ['P0', 'P1', 'P2', 'P3'],
                     'Q': ['Q0', 'Q1', 'Q2', 'Q3']}) 
data2 = pd.DataFrame({'key1': ['K0', 'K1', 'K1', 'K2'],
                      'key2': ['K0', 'K0', 'K0', 'K0'],
                      'R': ['R0', 'R1', 'R2', 'R3'],
                      'S': ['S0', 'S1', 'S2', 'S3']})
print("Original DataFrames:")
print(data1)
print("--------------------")
print(data2)
print("\nMerge two dataframes with different columns:")
result = pd.concat([data1,data2], axis=0, ignore_index=True)
print(result)

Sample Output:

Original DataFrames:
  key1 key2   P   Q
0   K0   K0  P0  Q0
1   K0   K1  P1  Q1
2   K1   K0  P2  Q2
3   K2   K1  P3  Q3
--------------------
  key1 key2   R   S
0   K0   K0  R0  S0
1   K1   K0  R1  S1
2   K1   K0  R2  S2
3   K2   K0  R3  S3

Merge two dataframes with different columns:
     P    Q    R    S key1 key2
0   P0   Q0  NaN  NaN   K0   K0
1   P1   Q1  NaN  NaN   K0   K1
2   P2   Q2  NaN  NaN   K1   K0
3   P3   Q3  NaN  NaN   K2   K1
4  NaN  NaN   R0   S0   K0   K0
5  NaN  NaN   R1   S1   K1   K0
6  NaN  NaN   R2   S2   K1   K0
7  NaN  NaN   R3   S3   K2   K0

For more Practice: Solve these Related Problems:

Write a Pandas program to merge two DataFrames that have different sets of columns and then fill missing columns with default values.
Write a Pandas program to combine two DataFrames with disparate columns using an outer join and then sort the final DataFrame by a common key.
Write a Pandas program to merge DataFrames with different column sets and then display the union of the columns in the output.
Write a Pandas program to perform a full outer merge on two DataFrames with different columns and then replace missing values with zeros.

Go to:

Previous: Write a Pandas program to combine the columns of two potentially differently-indexed DataFrames into a single result DataFrame.
Next: Write a Pandas program to Combine two DataFrame objects by filling null values in one DataFrame with non-null values from other DataFrame.

Python Code Editor:

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