How to Send ERC-20 Tokens using Web3.py and Python

Overview

In this guide, we explore how to transfer ERC-20 tokens on the Ethereum blockchain using Web3.py, a Python library for Ethereum interaction. ERC-20 tokens are a widely adopted standard for fungible tokens, powering decentralized applications (dApps), DeFi protocols, and more.

By the end of this tutorial, you’ll learn how to:

Set up a Python environment for blockchain development.
Transfer ERC-20 tokens to another Ethereum address.
Approve a smart contract to spend tokens on your behalf.

Prerequisites

Before proceeding, ensure you have:

Python 3.9+ installed.
A basic understanding of Ethereum and smart contracts.
An Ethereum wallet (e.g., MetaMask) with access to your private key.
A QuickNode endpoint (free tier available) for blockchain connectivity.

Dependency	Version
Python	3.9.6+
Web3.py	6.18.0+

Understanding ERC-20 Tokens

ERC-20 tokens adhere to a standardized smart contract interface, enabling seamless interoperability across Ethereum-based platforms. Key functions include:

transfer() – Sends tokens to another address.
approve() – Authorizes a third party (e.g., a smart contract) to spend tokens.

👉 Learn more about ERC-20 token standards

Step-by-Step Guide

Step 1: Set Up Your QuickNode Endpoint

Sign up for a free QuickNode account here.
Deploy an Ethereum Sepolia endpoint (testnet recommended for practice).
Note your RPC URL—you’ll need it to connect to the blockchain.

Step 2: Install Web3.py

Install the library via pip:

pip install web3==6.18.0

Step 3: Transfer ERC-20 Tokens

Create a Python script (main.py) with the following code:

from web3 import Web3
import json

# Configure Web3 connection
RPC_URL = 'YOUR_QUICKNODE_ENDPOINT'
w3 = Web3(Web3.HTTPProvider(RPC_URL))

# Contract details
CONTRACT_ADDRESS = Web3.to_checksum_address('0xYourTokenContract')
TO_ADDRESS = '0xRecipientAddress'
PRIVATE_KEY = 'YourPrivateKey'  # Never expose in production!

# Load ABI (from Etherscan or the token's documentation)
with open('abi.json') as f:
    ABI = json.load(f)

contract = w3.eth.contract(address=CONTRACT_ADDRESS, abi=ABI)

# Build transaction
nonce = w3.eth.get_transaction_count(w3.eth.account.from_key(PRIVATE_KEY).address)
tx = contract.functions.transfer(TO_ADDRESS, w3.to_wei(1, 'ether')).build_transaction({
    'chainId': w3.eth.chain_id,
    'gas': 200000,
    'gasPrice': w3.eth.gas_price,
    'nonce': nonce,
})

# Sign and send
signed_tx = w3.eth.account.sign_transaction(tx, PRIVATE_KEY)
tx_hash = w3.eth.send_raw_transaction(signed_tx.rawTransaction)
print(f"Transaction Hash: {tx_hash.hex()}")

Step 4: Approve Token Spending

To authorize a smart contract (e.g., a DEX) to spend tokens:

SPENDER_CONTRACT = '0xSpenderAddress'
tx = contract.functions.approve(SPENDER_CONTRACT, w3.to_wei(100, 'ether')).build_transaction({
    'chainId': w3.eth.chain_id,
    'gas': 200000,
    'nonce': nonce + 1,  # Increment nonce for sequential transactions
})

FAQs

1. What’s the difference between `transfer()` and `approve()`?

transfer() sends tokens directly to an address.
approve() grants permission to another contract to withdraw tokens later.

2. How do I get testnet ETH for gas fees?

Use the QuickNode Multi-Chain Faucet to obtain Sepolia ETH.

3. Is it safe to share my private key?

Never share your private key. Use environment variables or secure vaults in production.

Best Practices

Gas Optimization: Use eth_gasPrice to avoid overpaying.
Error Handling: Check for revert reasons with try-except blocks.
Security: Store keys securely using tools like python-dotenv.

👉 Explore advanced Web3.py techniques

Final Thoughts

Mastering ERC-20 transfers with Web3.py opens doors to DeFi development, token swaps, and more. Experiment with different networks (e.g., Polygon, Arbitrum) and explore advanced features like batch transactions.

For further reading:

Got feedback? Let us know how we can improve this guide! 🚀