用python实现区块链系统

实现一个完整的区块链系统需要多个部分，包括区块、交易、钱包、网络传输等。下面是一个简单的示例代码，实现了一个简化版的区块链系统。

1. 定义区块类

import hashlib
import json
from time import time


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

    def calculate_hash(self):
        block_string = json.dumps(self.__dict__, sort_keys=True)
        return hashlib.sha256(block_string.encode()).hexdigest()

2. 定义区块链类

class Blockchain:
    def __init__(self):
        self.chain = [self.create_genesis_block()]

    def create_genesis_block(self):
        return Block(0, time(), "Genesis Block", "0")

    def get_latest_block(self):
        return self.chain[-1]

    def add_block(self, new_block):
        new_block.previous_hash = self.get_latest_block().hash
        new_block.hash = new_block.calculate_hash()
        self.chain.append(new_block)

    def is_chain_valid(self):
        for i in range(1, len(self.chain)):
            current_block = self.chain[i]
            previous_block = self.chain[i - 1]

            if current_block.hash != current_block.calculate_hash():
                return False

            if current_block.previous_hash != previous_block.hash:
                return False

        return True

3. 测试代码

blockchain = Blockchain()

blockchain.add_block(Block(1, time(), {"amount": 4}))
blockchain.add_block(Block(2, time(), {"amount": 8}))

print("Blockchain is valid: ", blockchain.is_chain_valid())

# 修改区块数据，测试区块链是否仍然有效
blockchain.chain[1].data = {"amount": 100}
print("Blockchain is valid: ", blockchain.is_chain_valid())

运行上面的测试代码，会输出以下结果：

Blockchain is valid:  True
Blockchain is valid:  False

以上是一个简化版的区块链系统实现，真正的区块链系统需要更复杂的设计和实现。