watch_src20_events

Watch SRC20 events with automatic key fetching

Watch SRC20 Transfer and Approval events for your wallet, automatically fetching your viewing key from the Directory contract via signed read.

Signatures

def watch_src20_events(
    w3: Web3,
    *,
    encryption: EncryptionState,
    private_key: PrivateKey,
    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(
    w3: AsyncWeb3,
    *,
    encryption: EncryptionState,
    private_key: PrivateKey,
    ...same keyword args...
) -> AsyncSRC20EventWatcher

Parameters

Parameter	Type	Default	Description
w3	Web3 / AsyncWeb3		Web3 instance with Seismic support
encryption	EncryptionState		Encryption state from wallet client
private_key	PrivateKey		Signing key for Directory signed read
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 (decryption, RPC)
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 seismic_web3 import PrivateKey, SEISMIC_TESTNET
from seismic_web3.src20 import watch_src20_events

pk = PrivateKey.from_hex_str(os.environ["PRIVATE_KEY"])
w3 = SEISMIC_TESTNET.wallet_client(pk)

with watch_src20_events(
    w3,
    encryption=w3.seismic.encryption,
    private_key=pk,
    on_transfer=lambda log: print(f"Transfer: {log.decrypted_amount}"),
) as watcher:
    input("Press Enter to stop...\n")

Notes

• Fetches your viewing key from Directory via get_viewing_key() on creation — raises ValueError if no key registered

• The watcher starts automatically; call .stop() or use context manager to clean up

• If you already have the viewing key, use watch_src20_events_with_key() to skip the signed read

See Also

• watch_src20_events_with_key — Watch with explicit key (no wallet needed)

• SRC20EventWatcher — Underlying sync watcher class

• register_viewing_key — Register a key first