Cancel

TxTypeCancel cancels the execution of the transaction with the same nonce in the transaction pool. This transaction type is useful when a submitted transaction seems unprocessed for a certain amount of time.

Import extend from web3py_ext to extend web3 to kaia web3

Import necessary utils from eth_account, web3py_ext and cytoolz

Create a Web3 instance with the specified kaia Baobab testnet URL

Also, you can change the provider URL from baobab to allthatnode

Load an account from private key

Send a value transfer tx. It will be in the tx pool and canceled before execution. The cancel tx will be failed if it is already executed.

Create an empty transaction of type TxType.CANCEL. You can use empty_tx util to get a tx with default fields filled.

Merge the from and nonce fields into the empty tx by using the merge util.

Make the nonce to be same with previously sent value transfer tx. You need to set the same tx nonce you want to cancel

Use fill_transaction to add more params to transaction object like gas limit...

Sign the cancel tx by user's private key

Recover the signer's address from the signature in signed tx

You can decode the RLP-encoded tx by the Account.decode_transaction util and if you want to make the output format pretty, use the to_pretty util

Send the tx to the blockchain. It will return the tx hash, which will be used to wait the receipt

The wait_for_transaction_receipt method returns the tx receipt if it is completed in the blockchain

Finally, get the result.

cancel_example.py


from web3py_ext import extend
from web3 import Web3
from eth_account import Account
from web3py_ext.transaction.transaction import (
    empty_tx,
    fill_transaction,
    TxType
)
from web3py_ext.utils.klaytn_utils import to_pretty
from cytoolz import merge
w3 = Web3(Web3.HTTPProvider(
    'https://public-en-kairos.node.kaia.io'
    ))
def web3_cancel_sign_recover():
    user1 = Account.from_key('0x0e4ca6d38096ad99324de0dde108587e5d7c600165ae4cd6c2462c597458c2b8')
    value_transfer_tx = empty_tx(TxType.VALUE_TRANSFER)
    value_transfer_tx = merge(value_transfer_tx, {
        'from':user1.address,
        'to':user1.address,
        'value':Web3.to_peb(10, "klay")
    })
    value_transfer_tx = fill_transaction(value_transfer_tx, w3)
    signed_tx = Account.sign_transaction(value_transfer_tx, user1.key)
    w3.eth.send_raw_transaction(signed_tx.rawTransaction)
    cancel_tx = empty_tx(TxType.CANCEL)
    cancel_tx = merge(cancel_tx, {
        'from' : user1.address,
        'nonce' : value_transfer_tx['nonce']
    })
    cancel_tx = fill_transaction(cancel_tx, w3)
    # sign the kaia specific transaction type with web3py
    signed_tx = Account.sign_transaction(cancel_tx, user1.key)
    print("\nraw transaction of signed tx:", signed_tx.rawTransaction.hex())
    recovered_tx = Account.recover_transaction(signed_tx.rawTransaction)
    print("\nrecovered sender address", recovered_tx)
    decoded_tx = Account.decode_transaction(signed_tx.rawTransaction)
    print("\ndecoded transaction:", to_pretty(decoded_tx))
    tx_hash = w3.eth.send_raw_transaction(signed_tx.rawTransaction)
    tx_receipt = w3.eth.wait_for_transaction_receipt(tx_hash)
    print('tx hash: ', tx_hash, 'receipt: ', tx_receipt)
web3_cancel_sign_recover()

output


❯ py cancel_example.py
raw transaction of signed tx: 0x38f86b82036f850ba43b740083026d1894a2a8854b1802d8cd5de631e690817c253d6a9153f847f8458207f5a0a559852e977476bfa6ba263a9c1f1f4b60608b82752d73a3f1162e341e7b5f06a07f12a242ad1cdbc08966e62af4c8749fc438e058b1344a4f11ba206f207ddc84
recovered sender address 0xA2a8854b1802D8Cd5De631E690817c253d6a9153
decoded transaction: {
  "type": 56,
  "nonce": 879,
  "gasPrice": 50000000000,
  "gas": 159000,
  "from": "0xA2a8854b1802D8Cd5De631E690817c253d6a9153",
  "signatures": [
    {
      "v": 2037,
      "r": 74789788593375966616662801192824717129914792416281096168085546212656613646086,
      "s": 57476654897736400463186412232435765147976539862827431359170424955204316028036
    }
  ],
  "chainId": 1001
}
tx hash:  0x3b1278d3748b638a41ffc40ed4cffc6c789ceffbd924f9b00ae7b53f26815686 receipt:  AttributeDict({'blockHash': HexBytes('0x672deecd07b84c2b524f160fccc6ce0d20486bdde914a7c7065e2de0ed723635'), 'blockNumber': 147364137, 'contractAddress': None, 'cumulativeGasUsed': 349674, 'effectiveGasPrice': 25000000000, 'from': '0xA2a8854b1802D8Cd5De631E690817c253d6a9153', 'gasUsed': 21000, 'logs': [], 'logsBloom': HexBytes('0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000'), 'status': 1, 'to': '0xA2a8854b1802D8Cd5De631E690817c253d6a9153', 'transactionHash': HexBytes('0x3b1278d3748b638a41ffc40ed4cffc6c789ceffbd924f9b00ae7b53f26815686'), 'transactionIndex': 3, 'type': 0})