Merge DataFrames of Different Lengths in Python

To merge dataframes of different length, we need to use the merge() method. Let’s say the following is our 1st DataFrame with length 4 −

dataFrame1 = pd.DataFrame(
   {
      "Car": ['BMW', 'Lexus', 'Audi', 'Jaguar']
   }
)

print("DataFrame1 ...\n",dataFrame1)
print("DataFrame1 length = ", len(dataFrame1))

Following is our 2nd DataFrame with length 6 −

dataFrame2 = pd.DataFrame(
   {
      "Car": ['BMW', 'Lexus', 'Audi', 'Mercedes', 'Jaguar', 'Bentley']
   }
)

print("\nDataFrame2 ...\n",dataFrame2) print("DataFrame2 length = ", len(dataFrame2))

Now, merge DataFrames using the merge() −

mergedRes = dataFrame2.merge(dataFrame1, how='left')

Example

Following is the code −

import pandas as pd
# Create DataFrame1
dataFrame1 = pd.DataFrame(
   {
      "Car": ['BMW', 'Lexus', 'Audi', 'Jaguar']
   }
)
print("DataFrame1 ...\n",dataFrame1)
# Find length of DataFrame1
print("DataFrame1 length = ", len(dataFrame1))
# Create DataFrame2
dataFrame2 = pd.DataFrame(
   {
      "Car": ['BMW', 'Lexus', 'Audi', 'Mercedes', 'Jaguar', 'Bentley']
   }
)
print("\nDataFrame2 ...\n",dataFrame2)
# Find length of DataFrame2
print("DataFrame2 length = ", len(dataFrame2))
# merge DataFrames
mergedRes = dataFrame2.merge(dataFrame1, how='left')
print("\nMerged data frame...\n", mergedRes)

Output

This will produce the following output −

DataFrame1 ...
      Car
0     BMW
1   Lexus
2    Audi
3  Jaguar
DataFrame1 length = 4

DataFrame2 ...
        Car
0       BMW
1     Lexus
2      Audi
3  Mercedes
4    Jaguar
5   Bentley
DataFrame2 length = 6

Merged data frame...
        Car
0       BMW
1     Lexus
2      Audi
3  Mercedes
4    Jaguar
5   Bentley