Lesson 12 - How to Rename Files in a Folder Using Python (Step-by-Step Guide)

🚀 Why Use Python to Rename Files?

If you’ve ever needed to rename a large number of files—images, documents, or data files—you know how time-consuming it can be to do it manually.

Python is a powerful tool that can help automate this process. With just a few lines of code, you can rename hundreds of files in seconds. Whether you're working on a data science project, organizing files for a website, or managing downloads, this guide is for you.

🧰 Prerequisites

To follow this tutorial, you only need:

• Python 3 installed on your system
  
  

• A folder with files you want to rename
  
  

• Basic knowledge of Python (optional – we explain everything!)
  
  

No need to install extra libraries!

Step-by-Step: Rename Files in a Folder Using Python

Let’s look at a basic script that renames all files in a folder using a numbered pattern like file_1.jpg, file_2.jpg, etc.

✅ Python Script:

import os

# Step 1: Define the folder path

folder_path = 'path/to/your/folder' # Change this to your actual path

# Step 2: Loop through each file in the folder

for index, filename in enumerate(os.listdir(folder_path)):

# Step 3: Get file extension (e.g., .jpg, .txt)

file_extension = os.path.splitext(filename)[1]

# Step 4: Create new filename

new_name = f"file_{index + 1}{file_extension}"

# Step 5: Get full paths

old_file = os.path.join(folder_path, filename)

new_file = os.path.join(folder_path, new_name)

# Step 6: Rename the file

os.rename(old_file, new_file)

print(f"Renamed: {filename} ➜ {new_name}")

🔄 Example Output

Let’s say your folder has the following files:

cat.jpg

dog.jpg

car.jpg

After running the script, they’ll be renamed to:

file_1.jpg

file_2.jpg

file_3.jpg

🧠 How It Works – Line by Line

Code Explanation:

import os

Imports the os module for file handling

os.listdir(folder_path)

Lists all files in the folder

os.path.splitext(filename)[1]

Gets the file extension

os.rename(old_file, new_file)

Renames each file

✨ Customizing File Names

You can change the renaming pattern to include:

🕒 Date and Time:

from datetime import datetime

date_str = datetime.now().strftime("%Y-%m-%d")

new_name = f"{date_str}_{index + 1}{file_extension}"

📂 File Prefix:

new_name = f"projectA_image_{index + 1}{file_extension}"

💡 Replace Original Name (Preserve Extension):

base_name = os.path.splitext(filename)[0]

new_name = f"{base_name}_renamed{file_extension}"

🧪 Pro Tip: Always Test First

Before running the script on important files, test it in a separate folder to avoid losing data. You can also print the proposed changes without renaming:

print(f"Will rename: {filename} ➜ {new_name}")

🛠️ Common Use Cases

• Renaming downloaded files
  
  

• Organizing photo galleries
  
  

• Preparing datasets for machine learning
  
  

• Cleaning up inconsistent file names
  
  

• Automating repetitive tasks in your workflow

💬 Final Thoughts

Renaming files in bulk is just one of the many things you can automate with Python. It saves time, eliminates human error, and is super satisfying once set up.

Learning simple automation like this can significantly boost your productivity and give you full control over your data and file management.