web3.py

🚀 Web3.py - Ethereum Python Library Guide

A Python library for interacting with Ethereum and EVM-compatible blockchains.

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🔧 Installation

  python -m pip install web3

  # You may need additional tools like geth or Infura for full functionality.

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🌐 Connect to Ethereum

1. Mainnet (via Infura)

  from web3 import Web3
  
  infura_url = "https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID"
  w3 = Web3(Web3.HTTPProvider(infura_url))
  print("Connected:", w3.is_connected())  # Check connection

2. Testnet (Sepolia)

  sepolia_url = "https://sepolia.infura.io/v3/YOUR_INFURA_PROJECT_ID"  # TESTNET
  w3 = Web3(Web3.HTTPProvider(sepolia_url))

3. Local Node (Ganache)

  w3 = Web3(Web3.HTTPProvider("http://127.0.0.1:7545"))

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💰 Wallet Interactions

Get Balance

  balance = w3.eth.get_balance("0xAddress")
  print("Balance:", w3.from_wei(balance, 'ether'), "ETH")

Send Transaction

  tx = {
      'nonce': w3.eth.get_transaction_count("0xSender"),
      'to': "0xReceiver",
      'value': w3.to_wei(0.01, 'ether'),
      'gas': 21000,
      'gasPrice': w3.eth.gas_price,
  }
  signed_tx = w3.eth.account.sign_transaction(tx, "YOUR_PRIVATE_KEY")
  tx_hash = w3.eth.send_raw_transaction(signed_tx.rawTransaction)
  print("TX Hash:", tx_hash.hex())

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📜 Smart Contracts

1. Setup Contract

  contract_address = "0xContractAddress"
  contract_abi = '[{"inputs":[], "name":"getValue", "outputs":[{"internalType":"uint256","name":"","type":"uint256"}], "type":"function"}]'
  contract = w3.eth.contract(address=contract_address, abi=contract_abi)

2. Call & Transact

Read (Call)

  value = contract.functions.getValue().call()
  print("Value:", value)

Write (Transact)

  tx = contract.functions.setValue(123).build_transaction({
      'nonce': w3.eth.get_transaction_count("0xSender"),
      'gas': 200000,
  })
  signed_tx = w3.eth.account.sign_transaction(tx, "YOUR_PRIVATE_KEY")
  w3.eth.send_raw_transaction(signed_tx.rawTransaction)

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🔍 Common Use Cases

Check Latest Block

  print("Latest Block:", w3.eth.get_block('latest').number)

Listen to Events

  event_filter = contract.events.ValueChanged.create_filter(fromBlock='latest')
  for event in event_filter.get_new_entries():
      print("Event:", event)

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⚠️ Security Notes

• Never hardcode private keys! Use environment variables.
• Test on testnets before mainnet.
• Use Web3.py v6+.

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Documentation

Get started in 5 minutes or take a tour of the library.

View the change log.

For additional guides, examples, and APIs, see the documentation.

Want to Help?

Want to file a bug, contribute some code, or improve documentation? Excellent! Read up on our guidelines for contributing, then check out issues that are labeled Good First Issue.

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Questions on Implementation or Usage?

Join the conversation in the Ethereum Python Community Discord.