Merge() missing 1 required positional argument: ‘right’

merge() missing 1 required positional argument: ‘right’

When you see the error message “merge() missing 1 required positional argument: ‘right'”, it means that the merge() function in Python Pandas requires the ‘right’ argument to be provided, but it is missing in the code.

The merge() function is used to combine two or more DataFrames into a single DataFrame based on a common column or index. It is a powerful tool in data manipulation and analysis.

The correct syntax for the merge() function is:

merged_dataframe = pd.merge(left, right, on='common_column')

Here, ‘left’ and ‘right’ are the DataFrames that you want to merge, and ‘common_column’ is the column name or a list of column names that exist in both DataFrames and will be used as the merging key.

Let’s see an example to better understand this error:

# Import the necessary libraries
import pandas as pd

# Create two sample DataFrames
df1 = pd.DataFrame({'A': [1, 2, 3], 'B': ['a', 'b', 'c']})
df2 = pd.DataFrame({'A': [4, 5, 6], 'B': ['d', 'e', 'f']})

# Incorrect usage of merge() function
merged_dataframe = pd.merge(df1)  # Missing 'right' argument

In this example, we have two DataFrames (df1 and df2) with columns ‘A’ and ‘B’. We want to merge them based on the common column ‘A’. However, when we try to merge df1 without specifying the ‘right’ argument, it results in the mentioned error. The correct code should be:

# Correct usage of merge() function
merged_dataframe = pd.merge(df1, df2, on='A')

By providing both df1 and df2, as well as specifying the common column name ‘A’, the merge() function will combine the DataFrames based on the matching values in column ‘A’.

Remember to always include the ‘right’ argument in the merge() function call to avoid this error.