watch_src20_events_with_key

Watch SRC20 events with an explicit viewing key

Watch SRC20 Transfer and Approval events using an explicit viewing key, without requiring wallet authentication.

Signatures

def watch_src20_events_with_key(
    w3: Web3,
    *,
    viewing_key: Bytes32,
    token_address: ChecksumAddress | None = None,
    on_transfer: TransferCallback | None = None,
    on_approval: ApprovalCallback | None = None,
    on_error: ErrorCallback | None = None,
    poll_interval: float = 2.0,
    from_block: int | str = "latest",
) -> SRC20EventWatcher

async def async_watch_src20_events_with_key(
    w3: AsyncWeb3,
    *,
    viewing_key: Bytes32,
    ...same keyword args...
) -> AsyncSRC20EventWatcher

Parameters

Parameter	Type	Default	Description
w3	Web3 / AsyncWeb3		Standard Web3 instance (no Seismic namespace needed)
viewing_key	Bytes32		32-byte AES-256 viewing key
token_address	ChecksumAddress | None	None	SRC20 contract to filter (None = all tokens)
on_transfer	Callback	None	Invoked for Transfer events
on_approval	Callback	None	Invoked for Approval events
on_error	Callback	None	Invoked on errors
poll_interval	float	2.0	Seconds between polls
from_block	int | "latest"	"latest"	Starting block

Returns

SRC20EventWatcher (sync) or AsyncSRC20EventWatcher (async) — already started.

Example

import os
from web3 import Web3
from seismic_web3 import Bytes32
from seismic_web3.src20 import watch_src20_events_with_key

w3 = Web3(Web3.HTTPProvider("https://gcp-1.seismictest.net/rpc"))
viewing_key = Bytes32(bytes.fromhex(os.environ["VIEWING_KEY"].removeprefix("0x")))

watcher = watch_src20_events_with_key(
    w3,
    viewing_key=viewing_key,
    on_transfer=lambda log: print(f"Transfer: {log.decrypted_amount}"),
)

# Later...
watcher.stop()

Notes

• Does not require EncryptionState or a wallet private key — only a plain Web3 instance and the viewing key

• No RPC call to Directory (unlike watch_src20_events which fetches the key)

• Useful when you have a shared viewing key or want to avoid the signed read

See Also

• watch_src20_events — Watch with automatic key fetch from Directory

• SRC20EventWatcher — Underlying sync watcher class

• get_viewing_key — Fetch a key to pass here