Alternatives to listen Events contract with web3.py?

Question

I'm facing some issue/bug on web3.py, I need to listen my event contract, but event logs are always empty. I know the following issue on Ganach-CLI but may be there is other alternative. I already tried the three followings solutions and no one works, have [] as output...

The new method with web3.py v4 :

my_filter = mycontract.events.<event_name>.createFilter({'fromBlock':0,'to':'latest'})
my_filter.get_all_entries()

The old method :

my_filter = mycontract.eventFilter('EventName',{'fromBlock':0,'toBlock':'latest'})
my_filter.get_all_entries()

And finally tried to build my own filter :

event_hexa = w3.sha3(text='EventTest(address indexed _seller, string indexed)').hex()
    
event_filter = w3.eth.filter({
'fromBlock':0,
'toBlock':'latest',
'address': mycontract_address,
'topics':[str(event_hexa)]
})

event_filter.get_all_entries()

So I would like to know if there are other way to listen events ? May be I missed out on something.
Or may be there is other test net provider than Ganach where feature to listen event is working ?

Thanks for the help !

Answer 1

Here is how you can decode an event in web3.py:

def decode(hash,index,params):
    event = {}
    index1 = 1
    index2 = 2
    log = eth.getTransactionReceipt(hash)['logs'][index]
    for param in params:
        if param['indexed']:
            event[param['name']] = int(log['topics'][index1],16)
            index1 += 1
        else:
            size = param['size']//4
            event[param['name']] = int(log['data'][index2:index2+size],16)
            index2 += size
    return event

Where eth is your Web3.eth instance.

Usage example:

hash = mycontract.func(x)

index = 0

params = [
    {'name': 'addr', 'size': 160, 'indexed': True},
    {'name': 'input', 'size': 256, 'indexed': False},
    {'name': 'output', 'size': 256, 'indexed': False},
]

event = decode(hash, index, params)

addr = event['addr']
input = event['input']
output = event['output']

If more than one event is emitted during the execution of the contract's function, then use index to indicate the index of the specific event that you want to decode (I've used 0 in the example above, assuming that there's only one event).