# block.py

import hashlib
import uuid


class Block(object):
 def __init__(self, data=None, previous_hash=None):
  self.identifier = uuid.uuid4().hex # 产生唯一标示
  self.nonce = None     # nonce值
  self.data = data      # 区块内容
  self.previous_hash = previous_hash # 父节点哈希值
  
 def hash(self, nonce=None):
  '''
  计算区块的哈希值
  '''
  message = hashlib.sha256()
  message.update(self.identifier.encode('utf-8'))
  message.update(str(nonce).encode('utf-8'))
  message.update(str(self.data).encode('utf-8'))
  message.update(str(self.previous_hash).encode('utf-8'))

  return message.hexdigest()

 def hash_is_valid(self, the_hash):
  '''
  校验区块哈希值有否有效
  '''
  return the_hash.startswith('0000')

 def __repr__(self):
  return 'Block<Hash: {}, Nonce: {}>'.format(self.hash(), self.nonce)

# 创建一个内容为hello world的内容块

block = Block('Hello World')
block

Block<Hash: 238a65a101c8829d7fc406eb78a71cfc19ad702b437e2c1be8d9061ddb81e900, Nonce: None>

block.hash_is_valid(block.hash())

False

block.hash(1)

'a6431938ba10270dfcfdf7a2371312446914fedadf79632c2c0adb3b463f4838'

# block.py

import hashlib
import uuid


class Block(object):
 def __init__(self, data=None, previous_hash=None):
  self.identifier = uuid.uuid4().hex # 产生唯一标示
  self.nonce = None     # nonce值
  self.data = data      # 区块内容
  self.previous_hash = previous_hash # 父节点哈希值
  
 def hash(self, nonce=None):
  '''
  计算区块的哈希值
  '''
  message = hashlib.sha256()
  message.update(self.identifier.encode('utf-8'))
  message.update(str(nonce).encode('utf-8'))
  message.update(str(self.data).encode('utf-8'))
  message.update(str(self.previous_hash).encode('utf-8'))

  return message.hexdigest()

 def hash_is_valid(self, the_hash):
  '''
  校验区块哈希值有否有效
  '''
  return the_hash.startswith('0000')

 def __repr__(self):
  return 'Block<Hash: {}, Nonce: {}>'.format(self.hash(self.nonce), self.nonce)
 
 
 '''
  新增挖矿函数
 '''
 def mine(self):
  # 初始化nonce为0
  cur_nonce = self.nonce or 0

  # 循环直到生成一个有效的哈希值
  while True:
   the_hash = self.hash(nonce=cur_nonce)
   if self.hash_is_valid(the_hash): # 如果生成的哈希值有效
    self.nonce = cur_nonce   # 保持当前nonce值
    break       # 并退出
   else:
    cur_nonce += 1 # 若当前哈希值无效，更新nonce值，进行加1操作

block = Block('Hello World')

# 挖矿，循环直至找到合适的nonce
block.mine()

# 打印
block

Block<Hash: 000087359d5264153d624556f0a0c6f25cba06e453975c1c02587862e823911b, Nonce: 64751>

class BlockChain(object):
 def __init__(self):
  self.head = None # 指向最新的一个区块
  self.blocks = {} # 包含所有区块的一个字典

 '''
  添加区块函数
 '''
 def add_block(self, new_block):
  previous_hash = self.head.hash() if self.head else None
  new_block.previous_hash = previous_hash

  self.blocks[new_block.identifier] = {
   'block': new_block,
   'previous_hash': previous_hash,
   'previous': self.head,
  }
  self.head = new_block

 def __repr__(self):
  num_existing_blocks = len(self.blocks)
  return 'Blockchain<{} Blocks, Head: {}>'.format(
   num_existing_blocks,
   self.head.identifier if self.head else None
  )

# 初始化
chain = BlockChain()

# 打印
chain

Blockchain<0 Blocks, Head: None>

# 添加区块
chain.add_block(block)

# 打印
chain

Blockchain<1 Blocks, Head: 364c0cf963384ca28a2763499a140405>

# 添加更多的区块

for i in range(6):
 new_block = Block(i)
 new_block.mine()
 chain.add_block(new_block)
 
# 打印
chain

Blockchain<7 Blocks, Head: e7cb24ec7acd42a4aaebe7faee9e0713>