python源码实例

class Block:  

    def __init__(self, index, previous_hash, timestamp, data, hash):  

        self.index = index  

        self.previous_hash = previous_hash  

        self.timestamp = timestamp  

        self.data = data  

        self.hash = hash  

def calculate_hash(index, previous_hash, timestamp, data):  

    value = str(index) + str(previous_hash) + str(timestamp) + str(data)  

    return hashlib.sha256(value.encode('utf-8')).hexdigest()  

def create_genesis_block():  

    return Block(0, "0", int(time.time()), "Genesis Block", calculate_hash(0, "0", int(time.time()), "Genesis Block"))  

def create_new_block(previous_block, data):  

    index = previous_block.index + 1  

    timestamp = int(time.time())  

    hash = calculate_hash(index, previous_block.previous_hash, timestamp, data)  

    return Block(index, previous_block.previous_hash, timestamp, data, hash)  

def is_chain_valid(blockchain):  

    for i in range(1, len(blockchain)):  

        current_block = blockchain[i]  

        previous_block = blockchain[i - 1]  

        if current_block.hash != calculate_hash(current_block.index, current_block.previous_hash, current_block.timestamp, current_block.data):  

            return False  

        if current_block.previous_hash != previous_block.hash:  

            return False  

    return True  

# 区块链初始化  

blockchain = [create_genesis_block()]  

previous_block = blockchain[0]  

# 添加新区块到区块链中  

for i in range(1, 10):  # 添加10个新区块到区块链中作为示例  

    blockchain.append(create_new_block(previous_block, f"Block #{i}"))  

    previous_block = blockchain[-1]  # 更新previous_block为最新添加的区块

这个代码示例定义了一个Block类，用于表示区块链中的每个区块。每个区块包含一个索引、前一个区块的哈希值、时间戳、数据和自己的哈希值。此外，代码中还定义了几个辅助函数来帮助创建新的区块、验证区块链的完整性等。