How to listen for events in Python?

Jerry_Ji · November 17, 2019, 5:49am

Could any kind soul please share a working version of how to listen for events in Python?

I hope this is more open-ended than my SO question –

Many thanks in advance.

mike · November 17, 2019, 5:12pm

Hi @Jerry_Ji, a good place to start is the Python Websockets library.

Using that library along with our eth_subscribe websocket connection using the logs subscription type, should allow you to listen to events in Python!

Let us know how this works for you.

Jerry_Ji · November 18, 2019, 9:28pm

It seems web3py’s createFilter() does work with Infura websocket endpoint. I’ve updated the issue on github with web3.py –

github.com/ethereum/web3.py

AttributeError: 'Contract' object has no attribute 'eventFilter'

opened 02:39AM - 17 Nov 19 UTC

closed 06:04PM - 21 Nov 19 UTC

jerryji

* Version: 5.3.0 * Python: 3.6.8 * OS: linux (Ubuntu 18.04) * `pip freeze` ou…tput ``` alembic==0.9.9 anyconfig==0.9.4 APScheduler==3.5.1 apturl==0.5.2 argh==0.26.2 arrow==0.13.0 asciidoc3==3.1.0.post4 asn1crypto==0.24.0 attrdict==2.0.0 attrs==17.4.0 base58==1.0.3 beautifulsoup4==4.6.0 bitcoin==1.1.42 blinker==1.4 Brlapi==0.6.6 certifi==2018.4.16 cffi==1.11.5 chardet==3.0.4 chrome-gnome-shell==0.0.0 click==6.7 cloudpickle==0.5.6 coincurve==7.1.0 command-not-found==0.3 contextlib2==0.5.5 cryptography==2.2.2 cupshelpers==1.0 cycler==0.10.0 cytoolz==0.10.1 dask==0.19.2 decorator==4.3.0 defer==1.0.6 distro-info===0.18ubuntu0.18.04.1 docopt==0.6.2 elasticsearch==6.3.1 eth-abi==2.0.0 eth-account==0.4.0 eth-hash==0.2.0 eth-keyfile==0.5.1 eth-keys==0.2.4 eth-rlp==0.1.2 eth-tester==0.1.0b23 eth-testrpc==1.3.3 eth-typing==2.2.0 eth-utils==1.8.0 ethereum==1.6.1 feedparser==5.2.1 flake8==3.5.0 Flask==1.0.2 Flask-APScheduler==1.10.1 Flask-Cors==3.0.8 Flask-DebugToolbar==0.10.1 Flask-Login==0.4.1 Flask-Mail==0.9.1 Flask-SQLAlchemy==2.3.2 Flask-SSE==0.2.1 Flask-Webpack==0.1.0 Flask-WTF==0.14.2 future==0.16.0 geographiclib==1.50 geopy==1.20.0 gevent==1.3.7 greenlet==0.4.15 grip==4.5.2 gunicorn==19.9.0 hexbytes==0.1.0 hiredis==1.0.0 html5lib==0.999999999 htmlmin==0.1.12 httplib2==0.9.2 idna==2.7 importlib-metadata==0.23 iotop==0.6 ipfshttpclient==0.4.12 ipython==5.5.0 ipython-genutils==0.2.0 itsdangerous==0.24 Jinja2==2.10 json-rpc==1.10.8 jsonschema==3.1.1 kazam==1.4.5 keyring==10.6.0 keyrings.alt==3.0 kiwisolver==1.0.1 language-selector==0.1 launchpadlib==1.10.6 lazr.restfulclient==0.13.5 lazr.uri==1.0.3 louis==3.5.0 lru-dict==1.1.6 lxml==4.2.1 macaroonbakery==1.1.3 Mako==1.0.7 Markdown==3.1.1 MarkupSafe==1.0 matplotlib==3.1.1 mccabe==0.6.1 meld==3.18.0 meld3==2.0.0 more-itertools==4.1.0 msgpack==0.5.4 multiaddr==0.0.8 mypy-extensions==0.4.3 neovim==0.2.1 netaddr==0.7.19 netifaces==0.10.4 networkx==2.2 nose==1.3.7 numpy==1.17.2 oauth==1.0.1 oauthlib==2.0.6 olefile==0.45.1 opencv-python==3.4.3.18 pandas==0.25.1 parsimonious==0.8.0 path-and-address==2.0.1 pathtools==0.1.2 pbkdf2==1.3 pexpect==4.2.1 pickleshare==0.7.4 Pillow==5.3.0 pluggy==0.6.0 pngquant==1.0.6 populus==2.2.0 prettytable==0.7.2 prompt-toolkit==1.0.15 protobuf==3.10.0 psutil==5.4.2 psycopg2==2.8.3 py==1.5.3 py-ecc==1.4.2 py-geth==2.0.1 py-solc==2.1.0 pycairo==1.16.2 pycodestyle==2.3.1 pycosat==0.6.3 pycparser==2.18 pycrypto==2.6.1 pycryptodome==3.9.3 pycups==1.9.73 pyethash==0.1.27 pyflakes==1.6.0 Pygments==2.2.0 pygobject==3.26.1 PyJWT==1.5.3 pylru==1.0.9 pymacaroons==0.13.0 PyNaCl==1.1.2 PyOpenGL==3.1.0 pyOpenSSL==17.5.0 pyparsing==2.2.1 pyRFC3339==1.0 pyrsistent==0.15.5 pysha3==1.0.2 pytest==3.5.0 python-apt==1.6.4 python-dateutil==2.7.1 python-debian==0.1.32 python-editor==1.0.3 python-xapp==1.0.0 python-xlib==0.20 pytz==2019.2 PyWavelets==1.0.0 pyxattr==0.6.0 pyxdg==0.25 PyYAML==3.12 pyzmq==17.1.2 redis==2.10.6 reportlab==3.4.0 repoze.lru==0.7 requests==2.19.1 requests-unixsocket==0.1.5 rlp==1.0.1 rq==0.12.0 rq-dashboard==0.3.12 scikit-image==0.14.0 scipy==1.1.0 screen-resolution-extra==0.0.0 scrypt==0.8.6 secp256k1==0.13.2 SecretStorage==2.3.1 semantic-version==2.6.0 setproctitle==1.1.10 simplegeneric==0.8.1 simplejson==3.13.2 six==1.11.0 slither-analyzer==0.4.0 SQLAlchemy==1.2.7 ssh-import-id==5.7 supervisor==4.0.4 system-service==0.3 systemd-python==234 toolz==0.9.0 toposort==1.5 traitlets==4.3.2 tzlocal==1.5.1 ubuntu-drivers-common==0.0.0 ufw==0.36 unattended-upgrades==0.1 unity-scope-calculator==0.1 unity-scope-chromiumbookmarks==0.1 unity-scope-colourlovers==0.1 unity-scope-devhelp==0.1 unity-scope-firefoxbookmarks==0.1 unity-scope-manpages==0.1 unity-scope-openclipart==0.1 unity-scope-texdoc==0.1 unity-scope-tomboy==0.1 unity-scope-virtualbox==0.1 unity-scope-yelp==0.1 unity-scope-zotero==0.1 unity-tweak-tool==0.0.7 urllib3==1.23 usb-creator==0.3.3 uWSGI==2.0.17 validate-email==1.3 varint==1.0.2 vidcutter==6.0.0 virtualenv==15.1.0 wadllib==1.3.2 watchdog==0.8.3 wcwidth==0.1.7 web3==5.3.0 webencodings==0.5 websockets==8.1 Werkzeug==0.14.1 WTForms==2.1 xkit==0.0.0 youtube-dl==2018.3.14 zipp==0.6.0 zope.interface==4.3.2 ``` ### What was wrong? ``` AttributeError: 'Contract' object has no attribute 'eventFilter' ``` when I run ```my_contract.eventFilter('TokenTransfer', {'filter': {'fromBlock': 0}})``` following the example in web3py latest doc https://web3py.readthedocs.io/en/latest/contracts.html#event-log-object ``` (Pdb) my_contract <web3._utils.datatypes.Contract object at 0x7f5ac8027a90> (Pdb) dir(my_contract) ['__annotations__', '__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', '_encode_constructor_data', '_find_matching_event_abi', '_find_matching_fn_abi', '_prepare_transaction', '_return_data_normalizers', 'abi', 'address', 'all_functions', 'asm', 'ast', 'bytecode', 'bytecode_runtime', 'caller', 'clone_bin', 'constructor', 'decode_function_input', 'dev_doc', 'encodeABI', 'events', 'factory', 'fallback', 'find_functions_by_args', 'find_functions_by_name', 'functions', 'get_fallback_function', 'get_function_by_args', 'get_function_by_name', 'get_function_by_selector', 'get_function_by_signature', 'interface', 'metadata', 'opcodes', 'src_map', 'src_map_runtime', 'user_doc', 'web3'] ``` ### How can it be fixed? Please update doc with the correct example. BTW, createFilter works fine with ganache-cli, but unfortunately is not supported by Infura websocket

I briefly looked into parsing logs myself but find it too much manual work duplicating createFilter