class Block: def __init__(self, index, transaction, previous_hash): self.index = index self.timestamp = time() self.previous_hash = previous_hash self.transaction = transaction def compute_hash(self): concat_str = str(self.index) + str(self.timestamp) + str(self.previous_hash) + str(self.transaction['author']) + str(self.transaction['genre']) hash_result = hasher.sha256(concat_str.encode('utf-8')).hexdigest() return hash_result def serialize(self): return { 'index': self.index, 'timestamp': self.timestamp, 'previous_hash': self.previous_hash, 'transaction': self.transaction }

这段代码定义了一个区块类Block，用于创建区块链上的区块对象。该类包含以下属性：

1. index：区块在区块链中的索引。

2. timestamp：区块生成的时间戳。

3. previous_hash：前一个区块的哈希值。

4. transaction：该区块包含的交易信息。

该类的初始化方法__init__()用于初始化区块对象的属性值。compute_hash()方法用于计算区块的哈希值，通常使用SHA-256算法进行计算。serialize()方法用于将区块序列化为字典格式，以便存储在区块链中。

通过定义区块类，我们可以轻松地在区块链上存储和管理交易信息。每个区块都包含有关交易的信息和前一个区块的哈希值，以确保交易的安全性和完整性。

相关问题

区块源代码_200行代码构建一个区块链

很高兴回答您的问题。下面是200行代码构建一个简单的区块链的示例：

import hashlib
import json
from time import time

class Blockchain(object):
    def __init__(self):
        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):
        """
        Create a new Block in the Blockchain

        :param proof: <int> The proof given by the Proof of Work algorithm
        :param previous_hash: (Optional) <str> Hash of previous Block
        :return: <dict> New Block
        """

        block = {
            'index': len(self.chain) + 1,
            'timestamp': time(),
            'transactions': self.current_transactions,
            'proof': proof,
            'previous_hash': previous_hash or self.hash(self.chain[-1]),
        }

        # Reset the current list of transactions
        self.current_transactions = []

        self.chain.append(block)
        return block

    def new_transaction(self, sender, recipient, amount):
        """
        Creates a new transaction to go into the next mined Block

        :param sender: <str> Address of the Sender
        :param recipient: <str> Address of the Recipient
        :param amount: <int> Amount
        :return: <int> The index of the Block that will hold this transaction
        """
        self.current_transactions.append({
            'sender': sender,
            'recipient': recipient,
            'amount': amount,
        })

        return self.last_block['index'] + 1

    @staticmethod
    def hash(block):
        """
        Creates a SHA-256 hash of a Block

        :param block: <dict> Block
        :return: <str>
        """

        # We must make sure that the Dictionary is Ordered, or we'll have inconsistent hashes
        block_string = json.dumps(block, sort_keys=True).encode()
        return hashlib.sha256(block_string).hexdigest()

    @property
    def last_block(self):
        return self.chain[-1]

    def proof_of_work(self, last_proof):
        """
        Simple Proof of Work Algorithm:
         - Find a number p' such that hash(pp') contains leading 4 zeroes, where p is the previous p'
         - p is the previous proof, and p' is the new proof

        :param last_proof: <int>
        :return: <int>
        """
        proof = 0
        while self.valid_proof(last_proof, proof) is False:
            proof += 1

        return proof

    @staticmethod
    def valid_proof(last_proof, proof):
        """
        Validates the Proof: Does hash(last_proof, proof) contain 4 leading zeroes?

        :param last_proof: <int> Previous Proof
        :param proof: <int> Current Proof
        :return: <bool> True if correct, False if not.
        """

        guess = f'{last_proof}{proof}'.encode()
        guess_hash = hashlib.sha256(guess).hexdigest()
        return guess_hash[:4] == "0000"

这是一个区块链的基本数据结构和功能。您可以使用该代码进行测试和开发。

（二）区块链的共识算法：PoS 及其 例子 代码 实现

PoS（Proof of Stake）是一种区块链的共识算法，它通过锁定一定数量的代币来决定区块的生成权，相比于 PoW（Proof of Work）更加节能且不容易被攻击。下面给出一个简单的 PoS 示例代码实现：

import hashlib
import random

class Block:
    def __init__(self, index, timestamp, data, previous_hash, validator):
        self.index = index
        self.timestamp = timestamp
        self.data = data
        self.previous_hash = previous_hash
        self.validator = validator
        self.hash = self.calculate_hash()

    def calculate_hash(self):
        return hashlib.sha256(str(self.index).encode('utf-8') + 
                              str(self.timestamp).encode('utf-8') + 
                              str(self.data).encode('utf-8') + 
                              str(self.previous_hash).encode('utf-8') +
                              str(self.validator).encode('utf-8')).hexdigest()

class Blockchain:
    def __init__(self):
        self.chain = [self.create_genesis_block()]
        self.nodes = []
    
    def create_genesis_block(self):
        return Block(0, '01/01/2020', 'Genesis Block', '0', None)
    
    def add_node(self, node):
        self.nodes.append(node)
    
    def get_validator(self):
        total_stake = sum([node.stake for node in self.nodes])
        winning_num = random.uniform(0, total_stake)
        current_num = 0
        for node in self.nodes:
            current_num += node.stake
            if current_num > winning_num:
                return node
    
    def add_block(self, data):
        previous_block = self.chain[-1]
        validator = self.get_validator()
        new_block = Block(len(self.chain), 
                          str(datetime.datetime.now()), 
                          data, 
                          previous_block.hash, 
                          validator)
        self.chain.append(new_block)
        print(f"Block {new_block.index} has been added to the chain by {validator.name}.\n")

class Node:
    def __init__(self, name, stake):
        self.name = name
        self.stake = stake

if __name__ == '__main__':
    blockchain = Blockchain()
    node1 = Node('Alice', 100)
    node2 = Node('Bob', 50)
    node3 = Node('Charlie', 150)
    blockchain.add_node(node1)
    blockchain.add_node(node2)
    blockchain.add_node(node3)

    blockchain.add_block('Transaction A')
    blockchain.add_block('Transaction B')
    blockchain.add_block('Transaction C')

在上面的代码中，我们定义了一个 Block 类来表示区块，包含索引、时间戳、数据、前一个区块的哈希值和验证者等属性，以及一个 calculate_hash 方法来计算区块的哈希值。同时，我们还定义了一个 Blockchain 类来表示区块链，包含链和参与 PoS 共识的节点列表两个属性，以及 create_genesis_block、add_node、get_validator、add_block 等方法。其中，get_validator 方法用于随机选择一个验证者节点，add_block 方法用于添加新的区块并指定验证者。最后，在主程序中我们创建了三个节点，并添加了三个区块，每个区块的验证者都是随机选择的。