OS Module in Python

Python os Module – Complete Guide With Practical Examples

The os module in Python is one of the most powerful modules used to interact with the operating system. It allows you to perform operations such as:

• Create new directories
• Change working directory
• Delete files and folders
• Rename files
• Walk through directories
• Get file size, metadata
• List files & folders

This module gives Python the ability to perform real system-level tasks similar to Windows Explorer or Linux Shell.

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Basic OS Module Program (Step-by-Step Explanation)

import os

# Create a folder
# os.mkdir("hello")

# Change directory
os.chdir("hello")

# Create a file inside the folder
f = open("hello1.txt", "w")
f.write("hello world")
f.close()

# Delete the file
os.remove("hello1.txt")

# Remove directory (if empty)
# os.rmdir("hello1")

# Print current working directory
print(os.getcwd())

# List all files in current directory
print(os.listdir())

# Print all files from a specific directory
location = 'd:/c/'

for file in os.listdir(location):
    # if file.endswith(".c"):
    print(os.path.join(location, file))

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Important OS Module Functions You Must Know

1. os.mkdir("folder") – Create directory

2. os.rmdir("folder") – Remove directory (must be empty)

3. os.remove("file") – Delete file

4. os.rename(old, new) – Rename a file or folder

5. os.listdir(path) – List everything inside folder

6. os.getcwd() – Get current working directory

7. os.chdir(path) – Change working directory

8. os.walk(path) – Traverse all folders & subfolders

These functions are commonly used in file automation, cleaning scripts, backup scripts, and data mining tasks.

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Advanced Example – Count Files, Images, Videos, Python Programs & Largest File

The following program scans your entire drive (D:/ in this example) and counts:

• Total images
• Total text/doc files
• Total video files
• Total Python files
• Finds the largest file in the drive

import os

imgcount = 0
txtcount = 0
videocount = 0
pythonpgrm = 0

directory = 'd:/'
maxsize = 0
maxfilepath = ''

for root, dirs, files in os.walk(directory):

    for file in files:
        path = os.path.join(root, file)
        size = os.stat(path).st_size

        # Find largest file
        if maxsize < size:
            maxsize = size
            maxfilepath = path

        # Count image files
        if file.endswith('.png') or file.endswith('.jpg'):
            imgcount += 1
        
        # Count text and doc files
        elif file.endswith('.txt') or file.endswith('.docx'):
            txtcount += 1
        
        # Count audio/video files
        elif file.endswith('.mp3') or file.endswith('.mp4'):
            videocount += 1
        
        # Count python files
        elif file.endswith('.py'):
            pythonpgrm += 1

print("****** Scan Result for D Drive ******")
print("Total images       : " + str(imgcount))
print("Total text/docs    : " + str(txtcount))
print("Total video files  : " + str(videocount))
print("Total Python files : " + str(pythonpgrm))
print("Largest file path  : " + maxfilepath)
print("Largest file size  : " + str(maxsize) + " bytes")

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Extra Concepts Added for Better Understanding

1. Creating Nested Folders

os.makedirs("parent/child/grandchild")

2. Checking if a File Exists

import os

if os.path.exists("demo.txt"):
    print("File found")
else:
    print("File not found")

3. Getting File Size in KB / MB

size = os.stat("demo.txt").st_size
print(size/1024, "KB")
print(size/(1024*1024), "MB")

4. Rename Multiple Files Automatically

import os

for i, file in enumerate(os.listdir()):
    os.rename(file, f"image_{i}.jpg")

5. Searching for Files by Extension

import os

directory = "d:/"

for root, dirs, files in os.walk(directory):
    for file in files:
        if file.endswith(".pdf"):
            print(os.path.join(root, file))

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Assignments for OS Module

1. Count all folders in a drive.
2. Find the maximum size folder (not file).
3. Count total images in a specific directory.
4. Count all Python files in the entire computer.
5. Create a program to back up all .txt files to another folder.
6. Create an automatic renaming script for images.