Instance_Counter

A simple Python OOP project that automatically assigns a unique, incrementing ID to every instance of a class — useful for tracking, debugging, and managing how many objects you have created.

InstanceCounter uses a class-level counter that increments each time a new object is created. Every instance gets a unique ID that follows the order in which it was instantiated. The counter can be reset at any time via a static method.It also includes unit tests to verify correct behaviour.

Features

• Assigns a unique, automatically incrementing ID to each instance
• Supports resetting the class-level counter to zero
• Demonstrates Object-Oriented Programming (OOP) concept Encapsulation: the counter and ID logic are bundled inside the class, hidden from outside code.
• Demonstrates the difference between class variables (shared across all objects) and instance variables(unique to each object)
• Includes unit tests using Python’s unittest framework
• Supports Docker containerization
• Includes automated Docker build and run script
• Uses GitHub Actions for CI/CD automation

Requirements

• Python 3.x
• Docker Desktop
• Bash-compatible terminal (Git Bash, WSL, or Linux terminal)
• No external libraries required (uses Python standard library only)

Project Structure

instance-counter/
│
├── .github/
│   └── workflows/
│       └── ci.yml          # GitHub Actions CI/CD workflow
├── counter.py            # Main class implementation
├── testcounter.py        # Unit tests
├── Dockerfile            # Docker container configuration
├── build.sh              # Automated Docker build and run script
├── requirements.txt      # Project requirements
└── README.md             # Project documentation            

How It Works

Each time an InstanceCounter object is created, a class-level variable is incremented and assigned to the instance as its unique ID.

Example Usage

import counter

instance1 = counter.InstanceCounter()
instance2 = counter.InstanceCounter()

print(instance.id)  # 1
print(instance.id)  # 2

counter.InstanceCounter.reset()
instance3 = counter.InstanceCounter()
print(instance3.id)  # 1

How to Run

1. Clone the repository

git clone https://github.com/MakhutsoPoto/Instance_Counter.git
cd instance-counter

2. Run the program

python counter.py

3. Running the Tests

python test_counter.py

Docker Support

This project can be built and executed inside a Docker container.

Build Docker image

docker build -t instance-counter .

Run Docker container

docker run --rm instance-counter

---

Build Script

The project employs shell script to automate the Docker build and execution process.

Run build script

./build.sh

The script:

• builds the Docker image
• runs the container
• removes the container after execution

CI/CD Pipeline

This project uses GitHub Actions to automate:

• unit testing
• Python dependencies installs
• Docker image builds

The workflow runs automatically on every push and pull request to the main branch.

Technologies Used

• Python 3
• Object-Oriented Programming (OOP)
• Unit Testing (unittest)
• Docker
• Bash Scripting
• Github Actions

Learning Outcomes

This project demonstrates understanding of:

• The difference between class variables and instance variables,when to use each
• Object lifecycle in Python
• Object Oriented Programming principles:Encapsulation
• Basic unit testing practices with Python's unittest framework
• Docker containerization fundamentals
• Basic automation using Bash scripting
• CI/CD automation with GitHub Actions