Python构建区块链的方法详解

block = {
    'index': 1,
    'timestamp': 1506057125.900785,
    'transactions': [
        {
            'sender': "8527147fe1f5426f9dd545de4b27ee00",
            'recipient': "a77f5cdfa2934df3954a5c7c7da5df1f",
            'amount': 5,
        }
    ],
    'proof': 324984774000,
    'previous_hash': "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824"
}

# block_chain.py
class Blockchain:
    def __init__(self) -> None:
        self.chain = []
        self.current_transactions = []
    def new_block(self):
        # Creates a new Block and adds it to the chain
        pass
    def new_transaction(self):
        # Adds a new transaction to the list of transactions
        pass
    @staticmethod
    def hash(block):
        # Hashes a Block
        pass
    @property
    def last_block(self):
        # Returns the last Block in the chain
        pass

class Blockchain(object):
    ...
    def new_transaction(self, sender, recipient, amount) -> int:
        self.current_transactions.append({
            'sender': sender,
            'recipient': recipient,
            'amount': amount,
        })
        return self.last_block['index'] + 1

import hashlib
import JSON
from time import time
class Blockchain:
    def __init__(self) -> None:
        self.chain = []
        self.current_transactions = []
        # Create the genesis block
        self.new_block(previous_hash=1, proof=100)
    def new_block(self, proof, previous_hash=None) -> dict:
        block = {
            'index': len(self.chain) + 1,
            'timestamp': time(),
            'transactions': self.current_transactions,
            'proof': proof,
            'previous_hash': previous_hash or self.hash(self.chain[-1]),
        }
        self.current_transactions = []
        self.chain.append(block)
        return block
    def new_transaction(self, sender, recipient, amount) -> int:
        self.current_transactions.append(
            {
                'sender': sender,
                'recipient': recipient,
                'amount': amount,
            }
        )
        return self.last_block['index'] + 1
    @property
    def last_block(self) -> dict:
        # Returns the last Block in the chain
        return self.chain[-1]
    @staticmethod
    def hash(block) -> str:       
        block_string = json.dumps(block, sort_keys=True).encode()
        return hashlib.sha256(block_string).hexdigest()

class Blockchain(object):
    def proof_of_work(self, last_proof) -> int:
        proof = 0
        while self.valid_proof(last_proof, proof) is False:
            proof += 1
        return proof
    @staticmethod
    def valid_proof(last_proof, proof) -> bool:
        guess = f'{last_proof}{proof}'.encode()
        guess_hash = hashlib.sha256(guess).hexdigest()
        return guess_hash[:4] == '0000'

from uuid import uuid4
from time import time
from textwrap import dedent
from flask import Flask, jsonify, request
from block_chain import Blockchain
# 实例化应用
app = Flask(__name__)
# 创建随机节点名称
node_identifier = str(uuid4()).replace('_', '')
# 实例化block_chain类
block_chain = Blockchain()
# 创建/mine端点
@app.route('/mine', methods=['GET'])
def mine():
    block_chain.new_transaction(
        sender="0",
        recipient=node_identifier,
        amount=1,
    )
    last_block = block_chain.last_block
    last_proof = last_block['proof']
    proof = block_chain.proof_of_work(last_proof)
    previous_hash = block_chain.hash(last_block)
    block = block_chain.new_block(proof, previous_hash)
    response = {
        'message': "New Block Forged",
        'index': block['index'],
        'transactions': block['transactions'],
        'proof': block['proof'],
        'previous_hash': block['previous_hash'],
    }
    return jsonify(response), 200
@app.route('/transactions/new', methods=['POST'])
def new_transaction():
    return "We'll add a new transaction"
@app.route('/chain', methods=['GET'])
def full_chain():
    response = {
        'chain': block_chain.chain,
        'length': len(block_chain.chain),
    }
    return jsonify(response), 200
# 修改端口号
if __name__ == '__main__':
    app.run(host='0.0.0.0', port=5000)

...
from urllib.parse import urlparse
...
class Blockchain:
    def __init__(self) -> None:
        ...
        self.nodes = set()
        ...
    def reGISter_node(self, address) -> None:    
        parsed_url = urlparse(address)
        self.nodes.add(parsed_url.netloc)

...
import requests
class Blockchain:
    ...
    def valid_chain(self, chain):
        last_block = chain[0]
        current_index = 1
        while current_index < len(chain):
            block = chain[current_index]
            print(f'{last_block}')
            print(f'{block}')
            print("\n-----------\n")
            # Check that the hash of the block is correct
            if block['previous_hash'] != self.hash(last_block):
                return False
            # Check that the Proof of Work is correct
            if not self.valid_proof(last_block['proof'], block['proof']):
                return False
            last_block = block
            current_index += 1
        return True
    def resolve_conflicts(self):
        """
        This is our Consensus AlGorithm, it resolves conflicts
        by replacing our chain with the longest one in the network.
        :return: <bool> True if our chain was replaced, False if not
        """
        neighbours = self.nodes
        new_chain = None
        # We're only looking for chains longer than ours
        max_length = len(self.chain)
        # Grab and verify the chains from all the nodes in our network
        for node in neighbours:
            response = requests.get(f'Http://{node}/chain')
            if response.status_code == 200:
                length = response.json()['length']
                chain = response.json()['chain']
                # Check if the length is longer and the chain is valid
                if length > max_length and self.valid_chain(chain):
                    max_length = length
                    new_chain = chain
        # Replace our chain if we discovered a new, valid chain longer than ours
        if new_chain:
            self.chain = new_chain
            return True
        return False

@app.route('/nodes/register', methods=['POST'])
def register_nodes():
    values = request.get_json()
    nodes = values.get('nodes')
    if nodes is None:
        return "Error: Please supply a valid list of nodes", 400
    for node in nodes:
        blockchain.register_node(node)
    response = {
        'message': 'New nodes have been added',
        'total_nodes': list(blockchain.nodes),
    }
    return jsonify(response), 201
@app.route('/nodes/resolve', methods=['GET'])
def consensus():
    replaced = blockchain.resolve_conflicts()
    if replaced:
        response = {
            'message': 'Our chain was replaced',
            'new_chain': blockchain.chain
        }
    else:
        response = {
            'message': 'Our chain is authoritative',
            'chain': blockchain.chain
        }
    return jsonify(response), 200