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eth-event

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Tools for Ethereum event decoding and topic generation.

Installation

You can install the latest release via pip:

pip install eth-event

Or clone the repository and use setuptools for the most up-to-date version:

git clone https://github.com/iamdefinitelyahuman/eth-event.git
cd eth-event
python3 setup.py install

Usage

The public API is well documented within the docstrings. The following example may also help:

>>> from eth_event import get_topic_map

# generating a topic map
>>> abi = open('abi.json').read()
>>> topic_map = get_topic_map(abi)
>>> topic_map
{
    '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef': {
        'name': 'Transfer',
        'inputs': [
            {'name': 'from', 'type': 'address', 'indexed': True},
            {'name': 'to', 'type': 'address', 'indexed': True},
            {'name': 'value', 'type': 'uint256', 'indexed': False}
        ]
    }
}

# decoding event logs from a transaction receipt
>>> tx = token.transfer(account[1], 100, {'from': account[0]})
<Transaction object '0x615a157e84715d5f960a38fe2a3ddb566c8393cfc71f15b06170a0eff74dfdde'>
>>> eth_event.decode_logs(tx.logs, topic_map)
[{
    'name': 'Transfer',
    'address': "0x3194cBDC3dbcd3E11a07892e7bA5c3394048Cc87",
    'data': [
        {'name': 'from', 'type': 'address', 'value': '0xbd4940951bfa463f8fb6db762e55686f6cfdb73a', 'decoded': True},
        {'name': 'to', 'type': 'address', 'value': '0xbd4940951bfa463f8fb6db762e55686f6cfdb73a', 'decoded': True},
        {'name': 'tokens', 'type': 'uint256', 'value': 100, 'decoded': True}
    ],
    'logIndex': 0,
    'blockNumber': 0,
    'transactionIndex': 0
}]

# decoding a structLog from Geth's debug_traceTransaction endpoint
>>> trace = web3.provider.make_request(
    "debug_traceTransaction",
    ['0x615a157e84715d5f960a38fe2a3ddb566c8393cfc71f15b06170a0eff74dfdde', {}]
)
>>> struct_log = trace['result']['structLogs']

>>> eth_event.decode_trace(struct_log, topic_map, initial_address="0x3194cBDC3dbcd3E11a07892e7bA5c3394048Cc87")
[{
    'name': 'Transfer',
    'address': "0x3194cBDC3dbcd3E11a07892e7bA5c3394048Cc87",
    'data': [
        {'name': 'from', 'type': 'address', 'value': '0xbd4940951bfa463f8fb6db762e55686f6cfdb73a', 'decoded': True},
        {'name': 'to', 'type': 'address', 'value': '0xbd4940951bfa463f8fb6db762e55686f6cfdb73a', 'decoded': True},
        {'name': 'tokens', 'type': 'uint256', 'value': 100, 'decoded': True}
    ],
}]

Limitations

  • If an array is indexed in an event, the topic is generated as a sha3 hash and so cannot be decoded. In this case, the undecoded topic is returned and decoded is set to False.

  • Anonymous events cannot be decoded. Use the allow_undecoded kwarg when calling decode_logs and decode_trace to receive the undecoded log without raising an exception.

  • When decoding a trace, the initial address for the call cannot be determined. To include addresses where decoded events were emitted you must supply the initial address with the initial_address keyword argument.

Tests

To run the test suite:

$ tox

Development

This project is still in development. Comments, questions, criticisms and pull requests are welcomed.

License

This project is licensed under the MIT license.