创建区块链

# Python 提供的module（模組）與package（套件）是建立架構的基本元件
# Python的hashlib提供了常见的摘要算法，如MD5，SHA1等等。 摘要算法又称哈希算法、散列算法
import hashlib as hasher
# 該日期時間模塊類用來處理日期和時間
import datetime as date

# 定義一個類名為Block
class Block:
    # 初始化：用def命令定義初始化函數init，構造自身身份，索引，時間戳，數據，前哈希值
    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.hash_block()
    # 製造哈希值：用def命令定義
    def hash_block(self):
        # 此處用SHA256加密方法
        sha = hasher.sha256()
        sha.update(
            bytes(
                str(self.index) + str(self.timestamp) + str(self.data) + str(
                    self.previous_hash), 'utf-8'))
        return sha.hexdigest()

# 創造創世區塊
def create_genesis_block():
    # 手動構造一個索引為0和任意先前哈希的塊
    return Block(0, date.datetime.now(), "Genesis Block", "0")

# 構造區塊直接的連式結構，構造“區塊鏈”
def next_block(last_block):
    # 索引加一
    this_index = last_block.index + 1
    # 增加時間戳
    this_timestamp = date.datetime.now()
    # 增加區塊裡面的內容
    this_data = "Hey! I'm block " + str(this_index)
    # 哈希值指向前一個區塊的哈希值
    this_hash = last_block.hash
    # 返回區塊
    return Block(this_index, this_timestamp, this_data, this_hash)

# 創建區塊鏈並添加genesis塊
blockchain = [create_genesis_block()]
previous_block = blockchain[0]

# 在生成區塊之後，我們應該在鏈中增加的區塊數
num_of_blocks_to_add = 20

#通過循環鏈式添加區塊，使其成為有20個區塊的區塊鏈
for i in range(0, num_of_blocks_to_add):
    #將前後區塊鏈鏈接到一起
    block_to_add = next_block(previous_block)
    #用append方法增加區塊
    blockchain.append(block_to_add)
    #構造連式結構
    previous_block = block_to_add
    #  打印已經構造好的鏈
    print("Block #{} has been added to the "
            "blockchain!".format(block_to_add.index))
    print("Hash: {}\n".format(block_to_add.hash))