🧱 Simple Blockchain with Transactions in Python

A minimal blockchain implementation in Python featuring transaction support, Proof of Work, and a RESTful API powered by Flask.

🚀 Features

Blockchain data structure with block linking via hashes.

Simple Proof of Work (PoW) algorithm.

Transaction pool integrated into mined blocks.

RESTful API with endpoints to mine, view the chain, validate it, and add transactions.

Demonstrates fundamental blockchain concepts.

📝 Key Endpoints

Endpoint Method Description

/mine_block	        GET	Mines a new block and adds it to chain
/get_chain	        GET	Retrieves the full blockchain
/is_valid	        GET	Validates the blockchain integrity
/add_transaction	POST	Adds a new transaction

🛠️ How It Works

Blockchain Structure Each block contains:

index

timestamp

proof (Proof of Work)

previous_hash

transactions ✅

Transactions

Added via /add_transaction.

Stored in a pending transaction pool.

Included in the next mined block.

Proof of Work

Simple algorithm finding a number such that:

SHA256(new_proof² - previous_proof²) → hash starts with '00000'.

Validation

Ensures each block's hash correctly references its predecessor and PoW is valid.

▶️ Getting Started

Clone the repo:

git clone https://github.com/yourusername/blockchain-python.git
cd blockchain-python

Install dependencies:

pip install flask

Run the Flask app:

python blockchain.py

Access API at:

http://127.0.0.1:5000

📦 Example Usage

Add a transaction:

curl -X POST -H "Content-Type: application/json" \
-d '{"sender": "Alice", "recipient": "Bob", "amount": 50}' \
http://127.0.0.1:5000/add_transaction

Mine a block:

curl http://127.0.0.1:5000/mine_block

Check the chain:

curl http://127.0.0.1:5000/get_chain

🖼️ Blockchain Flow

[User Input]
  ↓
new_transaction(sender, recipient, amount)
  ↓
[Transactions Pool]
  ↓
mine_block()
  ↓
[Proof of Work]
  ↓
[create_block(proof, previous_hash, transactions)]
  ↓
[Append to Chain]
  ↓
[Clear Transactions]

🧪 Testing with Postman

Open Postman → New → HTTP Request.

Set method to POST.

URL: http://127.0.0.1:5000/add_transaction.

Body → raw → JSON:

{
  "sender": "Alice",
  "recipient": "Bob",
  "amount": 50
}

❓ Need Help?

If you get stuck, please refer to my page.

🏁 Summary

✅ Blockchain implemented from scratch.

✅ Transactions added to blocks.

✅ Simple Proof of Work.

✅ REST API via Flask.

✅ Testing with curl or Postman.

License

MIT