Event Listener functionality of the Web3.py doesn't register changes

Question

I am using the python implementation of the web3 library.(https://github.com/pipermerriam/web3.py) Calling and interacting with contracts works fine, but when it comes to the event listener functionality, none of the fired events are registered by the program.

def transfer_callback(log_entry): print "Event fired"

filter = contract.on("DisplayChange", {})

filter.watch(transfer_callback)

Watching the contracts event in the Ethereum Wallet also works without problems, so the issue is definitely connected to python. Thank you in advance for any response.

Answer 1

you might want to look at the docs here, the example is quite clear:

def new_transaction_callback(transaction_hash):
    sys.stdout.write("New Block: {0}".format(transaction_hash))

new_transaction_filter = web3.eth.filter('pending')
new_transaction_filter.watch(new_transaction_filter)
# each time the client receieves a unmined transaction the
# `new_transaction_filter` function will be called with the transaction
# hash.

another good place to look at examples on how it should be implemented is in the tests folder, specifically here

Answer 2

If you want to get contract event logs

def transfer_callback(log_entry): 
    print "Event fired"

contract = web3.eth.contract(abi, address)
contract.on("DisplayChange", {}, transfer_callback)