Ethereum: python for sending raw JSON-RPC HTTP requests to deploy and interact with a smart contract

AdditionContract.sol

pragma solidity ^0.4.18;

contract AdditionContract {
  uint public state = 0;

  function add(uint value1, uint value2) public {
    state = value1 + value2;
  }

  function getState() public constant returns (uint) {
      return state;
  }
}

raw_JSON_RPC_requests_to_smart_contract.py

# associated medium post: https://medium.com/@ethervolution/ethereum-create-raw-json-rpc-requests-with-python-for-deploying-and-transacting-with-a-smart-7ceafd6790d9
import requests
import json
import web3 # Release 4.0.0-beta.8
import pprint
import time

# create persistent HTTP connection
session = requests.Session()
w3 = web3.Web3()
pp = pprint.PrettyPrinter(indent=2)

requestId = 0 # is automatically incremented at each request

URL = 'http://localhost:8501' # url of my geth node
PATH_GENESIS = '/home/salanfe/privateNetworks/geth_PoA/genesis.json'
PATH_SC_TRUFFLE = '/home/salanfe/Projects/AdditionContract/' # smart contract path

# extracting data from the genesis file
genesisFile = json.load(open(PATH_GENESIS))
CHAINID = genesisFile['config']['chainId']
PERIOD  = genesisFile['config']['clique']['period']
GASLIMIT = int(genesisFile['gasLimit'],0)

# compile your smart contract with truffle first
truffleFile = json.load(open(PATH_SC_TRUFFLE + '/build/contracts/AdditionContract.json'))
abi = truffleFile['abi']
bytecode = truffleFile['bytecode']

# Don't share your private key !
myAddress = '0xF464A67CA59606f0fFE159092FF2F474d69FD675' # address funded in genesis file
myPrivateKey = '0x94cb9f766ef067eb229da85213439cf4cbbcd0dc97ede9479be5ee4b7a93b96f'


''' =========================== SOME FUNCTIONS ============================ '''
# see http://www.jsonrpc.org/specification
# and https://github.com/ethereum/wiki/wiki/JSON-RPC

def createJSONRPCRequestObject(_method, _params, _requestId):
    return {"jsonrpc":"2.0",
            "method":_method,
            "params":_params, # must be an array [value1, value2, ..., valueN]
            "id":_requestId}, _requestId+1
    
def postJSONRPCRequestObject(_HTTPEnpoint, _jsonRPCRequestObject):
    response = session.post(_HTTPEnpoint,
                            json=_jsonRPCRequestObject,
                            headers={'Content-type': 'application/json'})

    return response.json()

  
''' ======================= DEPLOY A SMART CONTRACT ======================= '''
### get your nonce
requestObject, requestId = createJSONRPCRequestObject('eth_getTransactionCount', [myAddress, 'latest'], requestId)
responseObject = postJSONRPCRequestObject(URL, requestObject)
myNonce = w3.toInt(hexstr=responseObject['result'])
print('nonce of address {} is {}'.format(myAddress, myNonce))

### create your transaction
transaction_dict = {'from':myAddress,
                    'to':'', # empty address for deploying a new contract
                    'chainId':CHAINID,
                    'gasPrice':1, # careful with gas price, gas price below the --gasprice option of Geth CLI will cause problems. I am running my node with --gasprice '1'
                    'gas':2000000, # rule of thumb / guess work
                    'nonce':myNonce,
                    'data':bytecode} # no constrctor in my smart contract so bytecode is enough

### sign the transaction
signed_transaction_dict = w3.eth.account.signTransaction(transaction_dict, myPrivateKey)
params = [signed_transaction_dict.rawTransaction.hex()]

### send the transacton to your node
requestObject, requestId = createJSONRPCRequestObject('eth_sendRawTransaction', params, requestId)
responseObject = postJSONRPCRequestObject(URL, requestObject)
transactionHash = responseObject['result']
print('contract submission hash {}'.format(transactionHash))

### wait for the transaction to be mined and get the address of the new contract
while(True):
    requestObject, requestId = createJSONRPCRequestObject('eth_getTransactionReceipt', [transactionHash], requestId)
    responseObject = postJSONRPCRequestObject(URL, requestObject)
    receipt = responseObject['result']
    if(receipt is not None):
        if(receipt['status'] == '0x1'):
            contractAddress = receipt['contractAddress']
            print('newly deployed contract at address {}'.format(contractAddress))
        else:
            pp.pprint(responseObject)
            raise ValueError('transacation status is "0x0", failed to deploy contract. Check gas, gasPrice first')
        break
    time.sleep(PERIOD/10)


''' ================= SEND A TRANSACTION TO SMART CONTRACT  ================'''
### get your nonce
requestObject, requestId = createJSONRPCRequestObject('eth_getTransactionCount', [myAddress, 'latest'], requestId)
responseObject = postJSONRPCRequestObject(URL, requestObject)
myNonce = w3.toInt(hexstr=responseObject['result'])
print('nonce of address {} is {}'.format(myAddress, myNonce))

### prepare the data field of the transaction
# function selector and argument encoding
# https://solidity.readthedocs.io/en/develop/abi-spec.html#function-selector-and-argument-encoding
value1, value2 = 10, 32 # random numbers here
function = 'add(uint256,uint256)' # from smart contract
methodId = w3.sha3(text=function)[0:4].hex()
param1 = (value1).to_bytes(32, byteorder='big').hex()
param2 = (value2).to_bytes(32, byteorder='big').hex()
data = '0x' + methodId + param1 + param2

transaction_dict = {'from':myAddress,
                    'to':contractAddress,
                    'chainId':CHAINID,
                    'gasPrice':1, # careful with gas price, gas price below the threshold defined in the node config will cause all sorts of issues (tx not bieng broadcasted for example)
                    'gas':2000000, # rule of thumb / guess work
                    'nonce':myNonce,
                    'data':data}

### sign the transaction
signed_transaction_dict = w3.eth.account.signTransaction(transaction_dict, myPrivateKey)
params = [signed_transaction_dict.rawTransaction.hex()]

### send the transacton to your node
print('executing {} with value {},{}'.format(function, value1, value2))
requestObject, requestId = createJSONRPCRequestObject('eth_sendRawTransaction', params, requestId)
responseObject = postJSONRPCRequestObject(URL, requestObject)
transactionHash = responseObject['result']
print('transaction hash {}'.format(transactionHash))

### wait for the transaction to be mined
while(True):
    requestObject, requestId = createJSONRPCRequestObject('eth_getTransactionReceipt', [transactionHash], requestId)
    responseObject = postJSONRPCRequestObject(URL, requestObject)
    receipt = responseObject['result']
    if(receipt is not None):
        if(receipt['status'] == '0x1'):
            print('transaction successfully mined')
        else:
            pp.pprint(responseObject)
            raise ValueError('transacation status is "0x0", failed to deploy contract. Check gas, gasPrice first')
        break
    time.sleep(PERIOD/10)



''' ============= READ YOUR SMART CONTRACT STATE USING GETTER  =============='''
# we don't need a nonce since this does not create a transaction but only ask
# our node to read it's local database

### prepare the data field of the transaction
# function selector and argument encoding
# https://solidity.readthedocs.io/en/develop/abi-spec.html#function-selector-and-argument-encoding
# state is declared as public in the smart contract. This creates a getter function
methodId = w3.sha3(text='state()')[0:4].hex()
data = '0x' + methodId
transaction_dict = {'from':myAddress,
                    'to':contractAddress,
                    'chainId':CHAINID,
                    'data':data}

params = [transaction_dict, 'latest']
requestObject, requestId = createJSONRPCRequestObject('eth_call', params, requestId)
responseObject = postJSONRPCRequestObject(URL, requestObject)
state = w3.toInt(hexstr=responseObject['result'])
print('using getter for public variables: result is {}'.format(state))



''' ============= READ YOUR SMART CONTRACT STATE GET FUNCTIONS  =============='''
# we don't need a nonce since this does not create a transaction but only ask
# our node to read it's local database

### prepare the data field of the transaction
# function selector and argument encoding
# https://solidity.readthedocs.io/en/develop/abi-spec.html#function-selector-and-argument-encoding
# state is declared as public in the smart contract. This creates a getter function
methodId = w3.sha3(text='getState()')[0:4].hex()
data = '0x' + methodId
transaction_dict = {'from':myAddress,
                    'to':contractAddress,
                    'chainId':CHAINID,
                    'data':data}

params = [transaction_dict, 'latest']
requestObject, requestId = createJSONRPCRequestObject('eth_call', params, requestId)
responseObject = postJSONRPCRequestObject(URL, requestObject)
state = w3.toInt(hexstr=responseObject['result'])
print('using getState() function: result is {}'.format(state))


''' prints
nonce of address 0xF464A67CA59606f0fFE159092FF2F474d69FD675 is 4
contract submission hash 0x64fc8ce5cbb5cf822674b88b52563e89f9e98132691a4d838ebe091604215b25
newly deployed contract at address 0x7e99eaa36bedba49a7f0ea4096ab2717b40d3787
nonce of address 0xF464A67CA59606f0fFE159092FF2F474d69FD675 is 5
executing add(uint256,uint256) with value 10,32
transaction hash 0xcbe3883db957cf3b643567c078081343c0cbd1fdd669320d9de9d05125168926
transaction successfully mined
using getter for public variables: result is 42
using getState() function: result is 42
'''