Events

Vyper emits up to five event logs. Each log contains both topics and data.

Topics (indexed arguments) are 32-byte description used to describe an event.They can be queried by listeners,and are identified by the indexed keyword.
Data (value arguments) do not have limitations. They can be complex data structures like arrays or strings.

Important thing to remember is that events are not stored in the state. They are only available to clients.

ℹ️ Note

Like Solidity, the first topic of the log record stores the event signature.

# pragma version 0.4.0

event SendEtherEvent:
    sender: indexed(address)
    recipient: indexed(address)
    value: uint256

@external
@payable
def sendEther(_recipient: address, _amount: uint256):
    assert _amount > 0, "Amount must be greater than 0"
    send(_recipient, _amount)

    # Emit event log
    log SendEtherEvent(msg.sender, _recipient, _amount)

Vyper Differentiators

Vyper event does not use emit but use log.

Events

Further Reading: