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Deploying a Vyper Smart Contract to Hedera Testnet using Python

Table of Contents

This guide walks through the process of deploying a smart contract to the Hedera testnet using Python and Web3.py. We'll be deploying a simple Vyper contract that demonstrates how to interact with the Hedera network.

Prerequisites

  • uv
    • You'll know you've done it right if you can run uv --version and see a version number.
  • git
    • You'll know you've done it right if you can run git --version and see a version number.
    • Helpful shortcut:
# For bash
echo "source $HOME/.bashrc >> $HOME/.bash_profile"

# For zsh
echo "source $HOME/.zshenv >> $HOME/.zprofile"
  • Python 3.x
  • A text editor
  • Basic understanding of smart contracts and Python
  • Hedera testnet account with HBAR (will show you how to get this)

Installation

git clone https://github.com/EdwinLiavaa/Web3py-Vyper-Hedera.git
cd Web3py-Vyper-Hedera

uv

uv sync

pip/python

python -m venv ./venv
source ./venv/bin/activate
pip install -r requirements.txt

Quickstart

uv run hello.py # for UV
# or
python hello.py # for pip/python

Setup Environment

First, let's set up our Python environment and install the necessary packages:

# Create and activate virtual environment
python3 -m venv .venv
source .venv/bin/activate

# Install required packages
pip install python-dotenv web3 vyper

Configuration

Create a .env file in your project root with your configuration:

RPC_URL="https://testnet.hashio.io/api"
PRIVATE_KEY="your-private-key"  # Never commit your real private key!
MY_ADDRESS="your-wallet-address"
ACCOUNT_ID="your-hedera-account-id"  # Format: 0.0.xxxxx

THIS IS ONLY FOR TESTING - TYPICALLY YOU SHOULD NEVER SHARE YOUR PRIVATE KEY.

Get Testnet HBAR

Before deploying, you'll need some testnet HBAR:

  1. Go to the Hedera Portal: https://portal.hedera.com/
  2. Create an account if you haven't already
  3. Your testnet account will automatically be credited with HBAR
  4. Save your Account ID and private key

The Smart Contract

Here's our simple Vyper contract (favorites.vy):

# @version ^0.3.7

favorite_number: public(uint256)
owner: public(address)

@external
def __init__():
    self.owner = msg.sender
    self.favorite_number = 0

@external
def store(new_number: uint256):
    self.favorite_number = new_number

Deployment Script

The deployment script (deploy_favorites_unsafe.py) handles the deployment to Hedera's testnet. Key features:

  • Uses Hedera's testnet RPC endpoint
  • Handles Hedera's address format
  • Manages gas fees in HBAR
  • Chain ID: 296 (Hedera Testnet)

Key Points About Hedera Deployment

  1. Network Configuration

  2. Address Format

    • Hedera uses both EVM-compatible addresses and Hedera account IDs
    • Account IDs format: 0.0.xxxxx
    • EVM addresses start with "0x"

  3. Gas Management

    • Gas fees are paid in HBAR
    • Gas limits are typically set to 3,000,000
    • Uses maxFeePerGas and maxPriorityFeePerGas for EIP-1559 style transactions

  4. Web3.py Compatibility

    • Uses web3.py's raw_transaction attribute for signed transactions
    • Ensures compatibility with latest web3.py versions
    • Properly handles transaction signing and sending

  5. Testing

    • Always test contracts on testnet first
    • Testnet HBAR is free from the Hedera Portal
    • Monitor your deployment using Hedera's testnet explorer

Troubleshooting

Common Issues

  1. SignedTransaction attribute error If you encounter an error like 'SignedTransaction' object has no attribute 'rawTransaction', make sure you're using:

    tx_hash = w3.eth.send_raw_transaction(signed_txn.raw_transaction)  # Note: raw_transaction not rawTransaction

    This is the correct attribute name in recent web3.py versions.

  2. Insufficient HBAR

    • Ensure you have enough testnet HBAR for deployment
    • Check your balance using the Hedera Portal
    • Request testnet HBAR if needed

  3. Network Connection Issues

    • Verify your RPC URL is correct
    • Check your internet connection
    • Ensure the Hedera testnet is operational

Running the Deployment

To deploy your contract:

  1. Ensure your .env file is configured with your Hedera credentials
  2. Make sure you have testnet HBAR
  3. Run the deployment script:
python deploy_favorites_unsafe.py

The script will:

  • Check your HBAR balance
  • Compile the Vyper contract
  • Deploy to Hedera testnet
  • Provide you with the deployed contract address

Special Thanks

The boilerplate used in this project was adopted from the Cyfrin Updraft Python and Viper Starter Kit: