ethereum-input-decorder

eth-defi-demo

A Python project demonstrating how to build decentralized finance (DeFi) applications using the eth_defi library. This project provides examples for connecting to EVM-compatible networks, interacting with ERC-20 tokens, reading on-chain data, executing swaps, and automating common DeFi workflows.

Features

• Connect to Ethereum-compatible RPC providers
• Load wallet from a private key
• Read ERC-20 token information
• Query balances
• Build and sign transactions
• Execute token transfers
• Perform Uniswap swaps
• Batch RPC requests using Multicall
• Estimate gas fees
• Listen for blockchain events
• Retry failed RPC requests
• Support multiple EVM chains

Requirements

• Python 3.10+
• pip
• Access to an Ethereum RPC endpoint

Examples:

• Infura
• Alchemy
• QuickNode
• Ankr
• Local Geth
• Local Anvil

Installation

git clone https://github.com/example/eth-defi-demo.git

cd eth-defi-demo

python -m venv .venv

source .venv/bin/activate      # Linux/macOS

# or

.venv\Scripts\activate         # Windows

pip install -r requirements.txt

requirements.txt

web3
web3-ethereum-defi
python-dotenv
requests

Project Structure

eth-defi-demo/
│
├── examples/
│   ├── connect.py
│   ├── wallet.py
│   ├── erc20.py
│   ├── transfer.py
│   ├── swap.py
│   ├── multicall.py
│   └── events.py
│
├── utils/
│   ├── config.py
│   ├── rpc.py
│   └── wallet.py
│
├── .env.example
├── requirements.txt
├── README.md
└── main.py

Configuration

Create a .env file.

RPC_URL=https://eth-mainnet.g.alchemy.com/v2/YOUR_API_KEY

PRIVATE_KEY=YOUR_PRIVATE_KEY

CHAIN_ID=1

Never commit your private key to Git.

Example

from web3 import Web3

rpc = "https://rpc.ankr.com/eth"

w3 = Web3(Web3.HTTPProvider(rpc))

print("Connected:", w3.is_connected())

print("Latest block:", w3.eth.block_number)

Reading ERC-20 Token Information

token_name = token.functions.name().call()

symbol = token.functions.symbol().call()

decimals = token.functions.decimals().call()

total_supply = token.functions.totalSupply().call()

Reading Wallet Balance

balance = w3.eth.get_balance(wallet)

print(w3.from_wei(balance, "ether"))

Token Transfer

tx = token.functions.transfer(
    recipient,
    amount
).build_transaction(...)

Swap Example

router.swap_exact_tokens_for_tokens(...)

Typical workflow:

• Approve token
• Build swap transaction
• Estimate gas
• Sign transaction
• Broadcast transaction
• Wait for receipt

Multicall

Instead of sending dozens of RPC requests:

balanceOf()
symbol()
decimals()
allowance()

Combine them into a single Multicall request for improved performance.

Event Listening

Example events:

• Transfer
• Approval
• Swap
• Mint
• Burn

Useful for:

• Wallet monitoring
• Trading bots
• Analytics
• Portfolio tracking

Supported Networks

• Ethereum
• Arbitrum
• Optimism
• Base
• Polygon
• BNB Chain
• Avalanche C-Chain
• Fantom
• Gnosis
• Scroll
• zkSync Era
• Linea

Security Recommendations

• Never hardcode private keys.
• Store secrets in environment variables.
• Validate contract addresses.
• Verify token decimals before transfers.
• Simulate transactions before broadcasting.
• Use HTTPS RPC providers.
• Limit wallet permissions.
• Protect API keys.

Common Use Cases

• Trading bots
• Arbitrage bots
• Portfolio trackers
• Yield farming automation
• Liquidity management
• Token analytics
• Wallet monitoring
• Blockchain indexing
• Treasury management
• DeFi dashboards

Troubleshooting

Connection failed

• Verify RPC endpoint.
• Check API key.
• Confirm internet connectivity.

Insufficient funds

Ensure the wallet has enough native tokens to pay gas fees.

Transaction reverted

Common causes include:

• Insufficient allowance
• Slippage exceeded
• Incorrect router address
• Expired deadline

Contributing

Contributions are welcome.

• Fork the repository.
• Create a feature branch.
• Commit your changes.
• Submit a pull request.

License

MIT License

Disclaimer

This project is provided for educational purposes only. Always test on a testnet before interacting with mainnet assets. You are responsible for securing your private keys and verifying all transactions before signing.