Simple Blockchain in Python

This is a fork of the 'Learn Blockchains by Building One' project by dvf. Make sure to check out his blog post on the same.

I re-implemented the same functionality for learning purposes. Along the way I made some improvements over the original codebase:

• Use Python 3.10
• Better code structure
• Define Models for Block and Transaction instead of passing them around as raw dictionaries
• Function type-annotations
• Use FastAPI instead of Flask
  • In our case, this mainly helps with easier request-response validation and auto generating the OpenAPI documentation.
• Make endpoints more RESTful
  • For eg. /mine/ endpoint must be a POST operation since it changes the server state.
• Move all business logic to the service layer
  • For eg. mining logic should reside in the Blockchain class instead of the endpoint function.
• Docker-compose file for spinning up multiple nodes at once

Installation

1. Pipenv

1. Make sure Python 3.10+ is installed.

2. Install pipenv.

   $ pip install pipenv

3. Install requirements

   $ pipenv install

4. Run some nodes:

   • $ pipenv run uvicorn src.node_server:app --port 8000
   • $ pipenv run uvicorn src.node_server:app --port 8001

2. Docker

Another option for running this program is to use Docker. Follow the instructions below to spawn two nodes.

1. Build the image

   $ docker-compose build

2. Run 2 nodes

   $ docker-compose up
   

3. To add more nodes, add more services to the docker-compose.yml

Testing

Tests can be run using pytest:

$ pipenv run pytest --cov=src

Potential Improvements

I made a note of some core blockchain features that are missing from this implementation. Interested readers can try working on these for a better understanding.

• Nodes using Public Key Infrastructure (such as for signing their transactions)
• Transaction Validation (person sending coins has the said amount or not?)
• Transaction Queuing (miners can work on transactions with a good payoff; at the same time the chain must make sure that no transactions starve)
• P2P communication between nodes
• Proof-of-Work Verification
• Mining difficulty proportional to remaining number of coins and the network's hash rate.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.