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# 使用Python实现一个简单的区块链下面是一个简单的区块链实现，包含区块结构、区块链类、工作量证明和基本的交易功能。 ```python import hashlib import json from time import time from typing import List, Dict, Any import uuid class Block: """区块类""" def __init__(self, index: int, transactions: List[Dict], timestamp: float, previous_hash: str, nonce: int = 0): self.index = index self.transactions = transactions self.timestamp = timestamp self.previous_hash = previous_hash self.nonce = nonce self.hash = self.calculate_hash() def calculate_hash(self) -> str: """计算区块的哈希值""" block_string = json.dumps({ "index": self.index, "transactions": self.transactions, "timestamp": self.timestamp, "previous_hash": self.previous_hash, "nonce": self.nonce }, sort_keys=True).encode() return hashlib.sha256(block_string).hexdigest() def __repr__(self) -> str: return f"Block(index={self.index}, hash={self.hash[:10]}..., previous_hash={self.previous_hash[:10]}..., transactions={len(self.transactions)})" class Blockchain: """区块链类""" def __init__(self, difficulty: int = 4): self.chain: List[Block] = [] self.difficulty = difficulty # 挖矿难度，表示哈希值前导零的数量 self.pending_transactions: List[Dict] = [] self.mining_reward = 100 # 挖矿奖励 # 创建创世区块 self.create_genesis_block() def create_genesis_block(self): """创建创世区块（第一个区块）""" genesis_block = Block(0, [], time(), "0") genesis_block.hash = genesis_block.calculate_hash() self.chain.append(genesis_block) def get_last_block(self) -> Block: """获取链上最后一个区块""" return self.chain[-1] def mine_pending_transactions(self, miner_address: str): """挖矿：将待处理交易打包成新区块""" # 添加挖矿奖励交易 reward_transaction = { "from": "network", "to": miner_address, "amount": self.mining_reward, "transaction_id": str(uuid.uuid4()) } self.pending_transactions.append(reward_transaction) # 创建新区块 block = Block( index=len(self.chain), transactions=self.pending_transactions, timestamp=time(), previous_hash=self.get_last_block().hash ) # 执行工作量证明 block = self.proof_of_work(block) # 将区块添加到链上 self.chain.append(block) # 清空待处理交易 self.pending_transactions = [] print(f"区块 #{block.index} 已成功挖出！奖励 {self.mining_reward} 给 {miner_address}") return block def proof_of_work(self, block: Block) -> Block: """工作量证明算法""" print(f"开始挖矿区块 #{block.index}...") # 不断尝试不同的nonce值，直到找到满足条件的哈希 while not self.is_valid_hash(block.hash): block.nonce += 1 block.hash = block.calculate_hash() print(f"挖矿完成！Nonce: {block.nonce}, Hash: {block.hash}") return block def is_valid_hash(self, hash: str) -> bool: """检查哈希值是否满足难度要求""" return hash[:self.difficulty] == "0" * self.difficulty def create_transaction(self, sender: str, recipient: str, amount: float) -> Dict: """创建交易""" transaction = { "from": sender, "to": recipient, "amount": amount, "transaction_id": str(uuid.uuid4()) } self.pending_transactions.append(transaction) print(f"交易已创建: {sender} 向 {recipient} 转账 {amount}") return transaction def get_balance(self, address: str) -> float: """获取地址余额""" balance = 0.0 for block in self.chain: for transaction in block.transactions: if transaction["from"] == address: balance -= transaction["amount"] if transaction["to"] == address: balance += transaction["amount"] return balance def is_chain_valid(self) -> bool: """验证区块链是否有效""" for i in range(1, len(self.chain)): current_block = self.chain[i] previous_block = self.chain[i-1] # 检查当前区块的哈希是否正确 if current_block.hash != current_block.calculate_hash(): print(f"区块 #{current_block.index} 的哈希值无效！") return False # 检查区块是否指向正确的前一个区块哈希 if current_block.previous_hash != previous_block.hash: print(f"区块 #{current_block.index} 的前一个哈希值无效！") return False # 检查工作量证明是否有效 if not self.is_valid_hash(current_block.hash): print(f"区块 #{current_block.index} 的工作量证明无效！") return False return True def display_chain(self): """显示整个区块链""" print("\n" + "="*60) print("区块链信息") print("="*60) print(f"链长度: {len(self.chain)}") print(f"挖矿难度: {self.difficulty}") print(f"挖矿奖励: {self.mining_reward}") print(f"区块链有效: {self.is_chain_valid()}") print("-"*60) for block in self.chain: print(f"\n区块 #{block.index}:") print(f" 哈希: {block.hash}") print(f" 前一个哈希: {block.previous_hash}") print(f" 时间戳: {block.timestamp}") print(f" Nonce: {block.nonce}") print(f" 交易数量: {len(block.transactions)}") if block.transactions: print(" 交易详情:") for tx in block.transactions: print(f" {tx['from']} -> {tx['to']}: {tx['amount']} (ID: {tx['transaction_id'][:8]}...)") # 演示区块链的使用 def demo_blockchain(): """演示区块链功能""" print("="*60) print("简单区块链演示") print("="*60) # 创建区块链 blockchain = Blockchain(difficulty=3) # 降低难度以便快速演示 # 创建一些交易 print("\n1. 创建交易...") blockchain.create_transaction("Alice", "Bob", 50) blockchain.create_transaction("Bob", "Charlie", 25) # 挖矿（由矿工Miner1执行） print("\n2. 开始挖矿...") blockchain.mine_pending_transactions("Miner1") # 创建更多交易 print("\n3. 创建更多交易...") blockchain.create_transaction("Charlie", "Alice", 10) blockchain.create_transaction("Alice", "David", 5) # 再次挖矿（由矿工Miner2执行） print("\n4. 再次挖矿...") blockchain.mine_pending_transactions("Miner2") # 显示区块链信息 blockchain.display_chain() # 显示余额 print("\n5. 地址余额:") addresses = ["Alice", "Bob", "Charlie", "David", "Miner1", "Miner2"] for address in addresses: balance = blockchain.get_balance(address) print(f" {address}: {balance}") # 验证区块链 print(f"\n6. 区块链有效: {blockchain.is_chain_valid()}") # 尝试篡改区块链 print("\n7. 尝试篡改区块链...") if len(blockchain.chain) > 1: # 修改第二个区块的第一笔交易 blockchain.chain[1].transactions[0]["amount"] = 1000 print(" 已修改区块 #1 的交易金额") print(f" 区块链有效: {blockchain.is_chain_valid()}") # 应该返回False if __name__ == "__main__": demo_blockchain() ``` ## 代码说明这个简单的区块链实现包含以下核心功能： ### 1. **区块结构 (Block类)** - `index`: 区块在链中的位置 - `transactions`: 区块包含的交易列表 - `timestamp`: 区块创建时间戳 - `previous_hash`: 前一个区块的哈希值

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