How to get the output of a function transaction using web3.py

Question

I have a smart contract that deploys another smart contract and returns the address of the deployed smart contract. The code for the smart contract looks like this-

contract ContractCreator {
    mapping(address=>address) deployedAddress;
    
    constructor() public {   
    }
    
    function createNFT(bytes32 _name) public returns(address){
        MyArtSale ob= new MyArtSale( _name, msg.sender);
        deployedAddress[msg.sender]=address(ob);
        return address(ob);
    }
    
    function fetchNFT () public view returns(address) {
        return deployedAddress[msg.sender];
    }
}

I want to interact with the createNFT function using web3.py and following is the python program-

truffleFile = json.load(open('./build/contracts/Ballot.json'))
abi = truffleFile['abi']
address = truffleFile['address']
contract= w3.eth.contract(address=address, abi=abi)

#building transaction
construct_txn = contract.functions.createCourse().buildTransaction({
    'from': acct.address,
    'nonce': w3.eth.getTransactionCount(acct.address),
    'gas': 1728712,
    'gasPrice': w3.toWei('50', 'gwei')})

signed = acct.signTransaction(construct_txn)

tx_hash=w3.eth.sendRawTransaction(signed.rawTransaction)
print(tx_hash.hex())
tx_receipt = w3.eth.waitForTransactionReceipt(tx_hash)

How can I access the address that is returned by the createNFT address using the python program

Answer 1

Transactions do not have return values, only function calls do. You need to emit events in your function and parse them from the transaction receipt section