code snippet to test ethereum filters

signal.sol

pragma solidity ^0.4.0;

contract Cui6 {
    event signal(uint indexed num);
    
    function testSignal() public {
        for (uint i=0; i<10; i++) {
            signal(i);
        }
    }
}

test_filter.py

import web3
from eth_abi import encode_single
from eth_utils import keccak

w3 = web3.Web3(web3.HTTPProvider("http://127.0.0.1:7545"))

getABI = lambda num: '0x'+encode_single('uint', num).hex()

topic = [getABI(num) for num in range(0, 50)]

filter = w3.eth.filter({"fromBlock":0, "toBlock":'latest', "topics":["0x"+keccak(b"signal(uint256)").hex(),topic]})

filter.get_all_entries()

while True:
    import time
    print(filter.get_new_entries())
    time.sleep(6)