Rename column by index Pandas in Python

One of the most used Python libraries for data science and machine learning is Pandas.

It offers a number of data exploration, cleaning, and transformation operations that are critical in working with data in Python.

Renaming columns in a Pandas DataFrame is a necessary task when working with datasets.

Pandas Library offers a straightforward way to achieve this. In this tutorial, we'll dive into how to rename columns using their index positions.

Understanding the DataFrame

Let's start by assuming we have a Pandas DataFrame df with columns we want to rename:

import pandas as pd

# Creating a sample DataFrame
data = {'A': [1, 2, 3],
        'B': [4, 5, 6],
        'C': [7, 8, 9]}

df = pd.DataFrame(data)
print(df)

Output:

   A  B  C
0  1  4  7
1  2  5  8
2  3  6  9

Renaming Columns by Index

Pandas provide df.columns attribute to get the column names of the DataFrame.

Lets say we want to rename the column 'A' to 'column_A'. We can do this by accessing the column name using its index position and assigning a new name to it.

Here is how we can do this:

# Renaming column by index
df.columns.values[0] = 'column_A'

print(df)

Output:

   column_A  B  C
0         1  4  7
1         2  5  8
2         3  6  9

As you can see, the column 'A' has been renamed to 'column_A'.

Renaming Multiple Columns by Index

Suppose we want to rename the columns 'A' and 'B' to 'column_A' and 'column_B' respectively.

You can assign a list of new column names to the df.columns.values attribute and adjust the index positions accordingly.

# Renaming multiple columns by index
df.columns.values[0:2] = ['column_A', 'column_B']

print(df)

Output:

   column_A  column_B  C
0         1         4  7
1         2         5  8
2         3         6  9

Renaming Columns Using a Loop

You can also rename columns using a loop. This is useful when you have a large number of columns to rename.

First create a list of new column names and then use a for loop to iterate over the list and rename the columns.

# Renaming columns using a loop
new_column_names = ['column_A', 'column_B', 'column_C']

for i in range(len(df.columns)):
    df.columns.values[i] = new_column_names[i]

print(df)

Output:

   column_A  column_B  column_C
0         1         4         7
1         2         5         8
2         3         6         9

Dynamically Renaming Columns by Index

For a large DataFrame, it is not feasible to rename columns one by one. You can use a for loop to rename columns dynamically.

Suppose we want to rename the columns 'A', 'B', and 'C' to 'A_new', 'B_new', and 'C_new' respectively.

# Appending 'New' to all column names
df.columns = [f'{col}_new' for col in df.columns]

print(df)

Output:

   A_new  B_new  C_new
0      1      4      7
1      2      5      8
2      3      6      9

Renaming column using rename()

The rename() method is used to rename any index, column or row. It accepts a dictionary as input, where the keys are the old column names and the values are the corresponding new column names.

Syntax:

df.rename(columns = {'old_column_name':'new_column_name'}, inplace=True)

Here, inplace=True saves the changes right away in the df dataset.

# Using rename() method to rename columns
df.rename(columns={'A': 'Alpha', 'B': 'Beta', 'C': 'Charlie'}, inplace=True)

print(df)

Output:

   Alpha  Beta  Charlie
0      1     4        7
1      2     5        8
2      3     6        9

Conclusion

In this section we covered renaming columns by index in Pandas, however, Pandas provides multiple approaches to renaming columns, catering to diverse needs and preferences.