Python implementation first block chain -blockchain

# 导入hashlib包
import hashlib
# 定义区块类
class Block:
    # 构造函数，包含4大属性
    def __init__(self,index,timestamp,data,previous_hash):
        # 前一个区块的哈希值
        self.previous_hash = previous_hash
        # 本区块所包含的数据
        self.data = data
        # 本区块所持有的时间戳
        self.timestamp = timestamp
        # 本区块的索引
        self.index = index
        # 本区块的哈希值
        self.hash = self.hash_block()

    # 求区块的哈希值
    def hash_block(self):
        sha = hashlib.sha256()
        sha.update((
            str(self.index)+
            str(self.timestamp)+
            str(self.data)+
            str(self.previous_hash)).encode("utf8")
        )
        return sha.hexdigest()


# 制作创世区块
import datetime
def create_genesis_block():
    return Block(0,datetime.datetime.now(),"Genesis Block","0")
# 制作下一个区块，last_block是上一个区块
def next_block(last_block):
    this_index = last_block.index+1
    this_timestamp = datetime.datetime.now()
    this_data = "Hey!I am block"+str(this_index)
    this_hash = last_block.hash
    return Block(this_index,this_timestamp,this_data,this_hash)
# 制作区块链
blockChain = [create_genesis_block()]
previous_block = blockChain[0]

# 创世区块之后，我们应该添加多少区块
num_of_blocks_to_add = 20
# 在区块链中添加区块
for i in range(num_of_blocks_to_add):
    block_to_add = next_block(previous_block)
    blockChain.append(block_to_add)
    previous_block = block_to_add
    # 打印区块链
    print("Block #{} has been added to the blockchain!".format(block_to_add.index))
    print("Hash:{}\n".format(block_to_add.hash))