15dkatz / python-blockchain-tutorial Goto Github PK

I am facing issue while replace chian, it's showng "Cannot replace chain: ... : The block last_hash must be correct"
I've tried various way, but chain is not replacing with local chain.

Can you please review my code in github repo, my github repo is given bellow.
https://github.com/sajjadhira/blockchain-development-using-python-javascript-reactjs

If i want to implement this on a p2p network, what will be the best way to implement that?

Hey,
I stumbled upon a problem with the default port 5000 on macOS Ventura (13.6.1).
In chapter 7.13 of the tutorial I get with:

export PEER=True && python3 -m backend.app

as requests.get result:

result: <Response [403]>

I found out (through stackoverflow) that macOS uses this port with the control center. It can be fixed by setting ROOT_PORT to some other value than 5000.

Great tutorial and maybe this info is of use to someone else!
Cheers

Can anyone know how to solve this error ??

Is there any specific reason or best practice, why use lambda instead directly using the existing function json.dumps in map

stringified_args = sorted(map(json.dumps, args)) 

Currently, the code to mine a block looks like this:

@app.route('/blockchain/mine')
def route_blockchain_mine():
  transaction_data = transaction_pool.transaction_data()
  transaction_data.append(Transaction.reward_transaction(wallet).to_json())
  blockchain.add_block(transaction_data)
  block = blockchain.chain[-1]
  pubsub.broadcast_block(block)
  transaction_pool.clear_blockchain_transactions(blockchain)

  return jsonify(block.to_json())

The problem here is that going to the /blockchain/mine endpoint causes the system to create a mining reward transaction even with an empty transaction pool. So a miner could keep hitting this endpoint over and over to get free coins.

The fix I made was to check and make sure there is a transaction to mine before handing out a mining reward; if the transaction pool is empty, the endpoint sends back a JSON message informing the miner that the transaction pool is empty.

@app.route('/blockchain/mine')
def route_blockchain_mine():
  transaction_data = transaction_pool.transaction_data()
  if transaction_data:
    transaction_data.append(Transaction.reward_transaction(wallet).to_json())
    blockchain.add_block(transaction_data)
    block = blockchain.chain[-1]
    pubsub.broadcast_block(block)
    transaction_pool.clear_blockchain_transactions(blockchain)

    return jsonify(block.to_json())
  return {"message": "Transaction pool is empty"}