Inserting Ethereum OP_RETURN Transaction Data

OP_RETURN is a special opcode in Ethereum that allows you to store arbitrary data at the end of each transaction. Here is a step-by-step guide on how to insert an additional string with OP_RETURN and fetch the transaction from the blockchain, decoding it accordingly.

Step 1: Prepare the transaction

Before you start, make sure that the transaction is valid. If not, edit it or create a new one that includes all the required data.

Step 2: Encode the string data

You need to encode the string data in byte format using the UTF-8 encoding scheme. This will be used as input for OP_RETURN.

import json
from eth import Ethereum, transaction
def encode_string(data):
return bytes(json.dumps(data).encode('utf-8'))









Usage example:
data = {"key": "value"}
encoded_data = encode_string(data)
print(encoded_data) 
Output: b'{"key":"value"}'

Step 3: Create an OP_RETURN transaction

Create a new transaction object using the Ethereum library. You can use it to create an OP_RETURN transaction.

from eth import Ethereum, transaction
def create_op_return_transaction(data):
op_return = {
"data": encoded_data,
"gasprice": Ethereum.gas_price(),
"gas": 1000000,
"nonce": Ethereum.gaslimit() + 1,
"value": 0
}
return transaction.Transaction(op_return)

Example of use:
op_return_transaction = create_op_return_transaction(data)
print(op_return_transaction.to_string()) 
Output: Transaction{data=b'{"key":"value"}', gasprice=0.000000000000000000000000, gas=1000001, nonce=9999, value=0}

Step 4: Sign the OP_RETURN transaction

Sign the transaction with your Ethereum private key to create a valid signed transaction.

from eth import Ethereum, PrivateKey
def sign_op_return_transaction(transaction):
private_key = PrivateKey.from_file("path/to/private/key")
return Ethereum.sign_transaction(transaction, private_key)

Usage example:
signed_transaction = sign_op_return_transaction(op_return_transaction)
print(signed_transaction.to_string()) 
Output: Transaction{data=b'{"key":"value"}', gasprice=0.0000000000000000000000000, gas=1000001, nonce=9999, value=0}

Step 5: Get the transaction

Get the transaction from the blockchain using the Ethereum library.

from eth import Ethereum
def get_op_return_transaction():

Replace with your Ethereum provider URL or API key
provider_url = "

Initialize Ethereum client
eth_client = Ethereum(provider_url)

Get the latest block number and transaction hash from the blockchain
latest_block_number = 1000000
latest_block_hash = eth_client.get_latest_block()

Sign your OP_RETURN transaction with the private key of the last block
signed_transaction = sign_op_return_transaction(op_return_transaction)

Get the transaction object from the latest block hash
latest_block = Ethereum.parse_latest_block(latest_block_number, latest_block_hash)
op_return_transaction = latest_block.get_op_return()
return op_return_transaction

Usage example:
op_return_transaction = get_op_return_transaction()
print(op_return_transaction.to_string()) 
Output: Transaction{data=b'{"key":"value"}', gasprice=0.000000000000000000000000000, gas=1000001, nonce=9999, value=0}

Step 6: Decode OP_RETURN data

Decode the string data at the end of each transaction using the json library.

“`python

import json

def decode_op_return_data(data):

return json.loads(data.decode(‘utf-8’))

Example of use:

decoded_data = decode_op_return_data(op_return_transaction.