how to get event data from web3py?

Question

pragma solidity ^0.4.17

contract Test {
    event greeting(string name);
    function say() pure public {
        greeting('jack');
    }
}

how to get the event data 'jack' when the say() function called in the python version web3.py? below is my python code.

contractAddress = '0x345ca3e014aaf5dca488057592ee47305d9b3e10'
contract = w3.eth.contract(address=contractAddress, abi=abiJson['abi'])
accounts = w3.eth.accounts

def handle_event(event):
    print(event)

def log_loop(event_filter, poll_interval):
    while True:
        for event in event_filter.get_new_entries():
            handle_event(event)
            time.sleep(poll_interval)

block_filter = w3.eth.filter({'fromBlock':'latest', 'address':contractAddress})
log_loop(block_filter, 2)

A lot more background would help: What happens when you run the code? What version of web3py are you using? What kind of node are you using? How are you triggering the event? — carver, Apr 16 '18 at 18:25

score 4 · Answer 1 · edited Aug 02 '22 at 18:35

The problem has been solved; the right code should be look like below:

contractAddress = '0x345ca3e014aaf5dca488057592ee47305d9b3e10'
contract = w3.eth.contract(address=contractAddress, abi=abiJson['abi'])
accounts = w3.eth.accounts

def handle_event(event):
    receipt = w3.eth.waitForTransactionReceipt(event['transactionHash'])
    result = contract.events.greeting.processReceipt(receipt)
    print(result[0]['args'])

def log_loop(event_filter, poll_interval):
    while True:
        for event in event_filter.get_new_entries():
            handle_event(event)
            time.sleep(poll_interval)

block_filter = w3.eth.filter({'fromBlock':'latest', 'address':contractAddress})
log_loop(block_filter, 2)

score 4 · Answer 2 · answered Apr 25 '21 at 12:56

I found your code really helpful to see how to extract the info of an event, but I faced an issue. I'll write it here just in case it can help anyone.

The line result = contract.events.greeting.processReceipt(receipt) was throwing the error: _parse_logs() missing 1 required positional argument: 'errors'

After some digging it seems to be a limitation of Web3py and it can be fixed with a previous instantiation of the event. So, the code would be:

contractAddress = '0x345ca3e014aaf5dca488057592ee47305d9b3e10'
contract = w3.eth.contract(address=contractAddress, abi=abiJson['abi'])
accounts = w3.eth.accounts
greeting_Event = contract.events.greeting() # Modification

def handle_event(event):
    receipt = w3.eth.waitForTransactionReceipt(event['transactionHash'])
    result = greeting_Event.processReceipt(receipt) # Modification
    print(result[0]['args'])

def log_loop(event_filter, poll_interval):
    while True:
        for event in event_filter.get_new_entries():
            handle_event(event)
            time.sleep(poll_interval)

block_filter = w3.eth.filter({'fromBlock':'latest', 'address':contractAddress})
log_loop(block_filter, 2)

how to get event data from web3py?

2 Answers2