Learn WEB3PY with Real Code Examples

from web3 import Web3

# Connect to local Ethereum node
w3 = Web3(Web3.HTTPProvider('http://127.0.0.1:8545'))

# Contract ABI and address (example)
abi = '[...]'
address = '0xYourContractAddress'
contract = w3.eth.contract(address=address, abi=abi)

# Read value from contract
value = contract.functions.getValue().call()
print('Contract value:', value)

# Send transaction to contract
tx_hash = contract.functions.setValue(42).transact({'from': w3.eth.accounts[0]})
w3.eth.wait_for_transaction_receipt(tx_hash)

A minimal example showing how to connect to Ethereum and interact with a deployed smart contract using Web3.py.

from web3 import Web3

w3 = Web3(Web3.HTTPProvider('http://127.0.0.1:8545'))
account = '0xYourAccountAddress'
balance = w3.eth.get_balance(account)
print('Balance:', w3.fromWei(balance, 'ether'), 'ETH')

Check the Ether balance of an account using Web3.py.

from web3 import Web3
from solcx import compile_source

w3 = Web3(Web3.HTTPProvider('http://127.0.0.1:8545'))

source_code = 'contract Simple { uint public x; function set(uint val) public { x = val; } }'
compiled = compile_source(source_code)
contract_interface = compiled['<stdin>:Simple']
Simple = w3.eth.contract(abi=contract_interface['abi'], bytecode=contract_interface['bin'])
tx_hash = Simple.constructor().transact({'from': w3.eth.accounts[0]})
tx_receipt = w3.eth.wait_for_transaction_receipt(tx_hash)
print('Contract deployed at:', tx_receipt.contractAddress)

Deploy a simple Solidity contract using Web3.py.

from web3 import Web3

w3 = Web3(Web3.HTTPProvider('http://127.0.0.1:8545'))
abi = '[...]'
address = '0xYourContractAddress'
contract = w3.eth.contract(address=address, abi=abi)

event_filter = contract.events.YourEvent.createFilter(fromBlock='latest')
for event in event_filter.get_new_entries():
    print(event)

Subscribe to events emitted by a smart contract.

from web3 import Web3

w3 = Web3(Web3.HTTPProvider('http://127.0.0.1:8545'))
from_account = w3.eth.accounts[0]
to_account = w3.eth.accounts[1]

tx = {
    'from': from_account,
    'to': to_account,
    'value': w3.toWei(0.1, 'ether'),
    'gas': 21000,
    'gasPrice': w3.toWei('50', 'gwei')
}
tx_hash = w3.eth.send_transaction(tx)
w3.eth.wait_for_transaction_receipt(tx_hash)

Send Ether from one account to another using Web3.py.

from web3 import Web3

w3 = Web3(Web3.HTTPProvider('http://127.0.0.1:8545'))
abi = '[...]'
address = '0xTokenContractAddress'
contract = w3.eth.contract(address=address, abi=abi)

# Check token balance
balance = contract.functions.balanceOf(w3.eth.accounts[0]).call()
print('Token Balance:', balance)

# Transfer tokens
tx_hash = contract.functions.transfer(w3.eth.accounts[1], 100).transact({'from': w3.eth.accounts[0]})
w3.eth.wait_for_transaction_receipt(tx_hash)

Read balance and transfer ERC20 tokens.

from web3 import Web3

w3 = Web3(Web3.HTTPProvider('http://127.0.0.1:8545'))
abi = '[...]'
address = '0xYourContractAddress'
contract = w3.eth.contract(address=address, abi=abi)

gas_estimate = contract.functions.setValue(42).estimateGas({'from': w3.eth.accounts[0]})
print('Estimated Gas:', gas_estimate)

Estimate gas required for a contract function call.

from web3 import Web3

w3 = Web3(Web3.HTTPProvider('http://127.0.0.1:8545'))
tx_hash = '0xYourTransactionHash'
receipt = w3.eth.get_transaction_receipt(tx_hash)
print(receipt)

Fetch and inspect a transaction receipt.

from web3 import Web3

w3 = Web3(Web3.HTTPProvider('http://127.0.0.1:8545'))
abi = '[...]'
address = '0xYourContractAddress'
contract = w3.eth.contract(address=address, abi=abi)

result = contract.functions.getValue().call()
print('Value:', result)

Call a read-only function from a deployed smart contract.

from web3 import Web3
from solcx import compile_source

w3 = Web3(Web3.HTTPProvider('http://127.0.0.1:8545'))
source = 'contract Greeter { string public greeting; constructor(string memory _g) { greeting = _g; } }'
compiled = compile_source(source)
contract_interface = compiled['<stdin>:Greeter']
Greeter = w3.eth.contract(abi=contract_interface['abi'], bytecode=contract_interface['bin'])
tx_hash = Greeter.constructor('Hello Web3').transact({'from': w3.eth.accounts[0]})
tx_receipt = w3.eth.wait_for_transaction_receipt(tx_hash)
print('Deployed at:', tx_receipt.contractAddress)

Deploy a Solidity contract providing constructor parameters.