学习用Python实现简单区块链
Python 实现区块链
环境
python3(本次用的3.8)、postman、requests、Flask，pip，pipenv等工具
环境步骤
-
先安装一个环境
pip install pipenv
pipenv使用 -
创建环境
pipenv install会生成一个pipfile文件，用于管理库的依赖 -
在虚拟环境中安装依赖
pipenv install flask==2.0.2
pipenv install requests==2.18.4
安装成功后可看到pipfile中看到
-
启动虚拟环境
pipenv shell -
新建一个blockchain.py 开始撸代码
代码思路
确定区块结构
{
"index":0, // 块序号
"timestamp":"",// 时间戳
"transactions":""[ // 交易信息
{
"sender":"",
"recipient":"",
"amount":5,
}
],
"proof":"", // 工作量证明
"previous_hash":"",// 前区块的哈希值
}
确定一下区块类功能
class Blockchain:
def __init__(self):
self.chain = [] # 存块
self.current_transactions = [] # 交易实体
def new_block(self): # 新建区块
pass
def new_transaction(self):# 新建交易
pass
@staticmethod
def hash(block):# 计算哈希值
pass
@property
def last_block(self):# 获取当前链中最后一个区块
pass
def proof_of_work(self):# 工作量证明计算
pass
def vaild_proof(self):# 验证计算值是否符合要求
pass
def vaild_chain(self):# 验证链是否符合要求
pass
def register_node(self):# 节点注册
pass
def resolve_conflicts:# 共识算法，解决冲突
pass
添加交易
def new_transaction(self, sender: str, recipient: str, amount: int) -> int:
"""添加新的交易
Args:
sender (str): 发送方
recipient (str): 接收方
amount (int): 金额
Returns:
int: 返回一个包含此交易的区块序号
"""
self.current_transactions.append({
'sender': sender,
'recipient': recipient,
'amount': amount
})
return self.last_block['index'] + 1
添加新块
def new_block(self, proof: int, previous_hash=None): # 新建区块
block = {
'index': len(self.chain) + 1,
'timestamp': time(),
'transactions': self.current_transactions,
'proof': proof,
'previous_hash': previous_hash or self.hash(self.last_block),
}
self.current_transactions = [] # 新建区块打包后重置当前交易信息
self.chain.append(block) # 把新建的区块加入链
return block
计算哈希值
@staticmethod
def hash(block: Dict[str, Any]) -> str:
"""计算哈希值,返回哈希后的摘要信息
Args:
block (Dict[str, Any]): 传入一个块
Returns:
str: 摘要信息
"""
block_string = json.dumps(block, sort_keys=True).encode()
return hashlib.sha256(block_string).hexdigest()
工作量证明与验证
def proof_of_work(self, last_proof: int) -> int:
"""工作量计算，计算一个符合要求的哈希值
Args:
last_proof (int): 上一个块的工作量随机数
Returns:
int: 返回符合要求的工作量随机数
"""
proof = 0
while self.valid_proof(last_proof, proof) is False:
proof += 1
# print(proof) 输出计算结果
return proof
def valid_proof(self, last_proof: int, proof: int) -> bool:
"""工作量证明验证，验证计算结果是否以2个0开头
Args:
last_proof (int): 前工作证明
proof (int): 当前工作证明
Returns:
bool: 返回验证是否有效
"""
guess = f'{last_proof}{proof}'.encode()
guess_hash = hashlib.sha256(guess).hexdigest()
# print(guess_hash) 输出计算过程
if guess_hash[0:2] == "00":
return True
else:
return False
验证一下，创建一个类，设定前一个工作量证明为100
尝试运行代码
可以看到这里算出前两位为0的就停止，结果为226
节点注册
def register_node(self, address: str) -> None:
"""添加一个新节点到节点集中
Args:
address (str): 节点的地址。Eg："http://127.0.0.1:5002"
"""
parsed_url = urlparse(address) # 解析url参数
self.nodes.add(parsed_url.netloc) # 获取域名服务器
共识算法
def resolve_conflicts(self) -> bool:
"""共识算法，解决冲突，以最长且有效的链为主
Returns:
bool: 冲突是否解决成功
"""
neighbours = self.nodes # 获取节点信息
new_chain = None # 定义可能的新链
max_length = len(self.chain) # 获取当前链长度
for node in neighbours: # 获取节点的链条信息，如果更长且有效则直接替换
response = requests.get(f'http://{node}/chain')
if response.status_code == 200:
length = response.json()['length']
chain = response.json()['chain']
if length > max_length and self.vaild_chain(chain):
max_length = length
new_chain = chain
if new_chain:
self.chain = new_chain
return True
return False
Web功能
使用flask 部署服务器
app = Flask(__name__)
if __name__ == "__main__":
app.run(host='0.0.0.0', port=5000)
尝试运行代码
从postman 中可看到一些信息，目前没有定义接口，自然是404
确定一下接口
@app.route('/transactions/new', methods=['POST'])
def new_transaction():
pass
@app.route('/mine', methods=['GET'])
def mine():
pass
@app.route('/chain', methods=['GET'])
def full_chain():
pass
@app.route('/nodes/register', methods=['POST'])
def register_nodes():
pass
@app.route('/nodes/resolve', methods=['GET'])
def consensus():
pass
交易接口
# 添加新建交易接口
@app.route('/transactions/new', methods=['POST'])
def new_transaction():
values = request.get_json()
required = ['sender', 'recipient', 'amount']
if not all(k in values for k in required):
return '确少参数', 400
index = blockchain.new_transaction(values['sender'], values['recipient'],
values['amount'])
response = {'message': f'交易将会被添加到块 {index}'}
return jsonify(response), 201
查看链接口
# 查看链接口
@app.route('/chain', methods=['GET'])
def full_chain():
response = {
'chain': blockchain.chain,
'length': len(blockchain.chain),
}
return jsonify(response), 200
打包区块接口
@app.route('/mine', methods=['GET'])
def mine():
last_block = blockchain.last_block # 获取链上最后一个区块的信息
last_proof = last_block['proof']
proof = blockchain.proof_of_work(last_proof)
# 发送者为 "0" 表明是新挖出的币,为矿工提供奖励
blockchain.new_transaction(
sender="0",
recipient=node_identifier,
amount=1,
)
block = blockchain.new_block(proof, None) # 生成一个新块
response = {
'message': "打包成功，新区块已生成！",
'index': block['index'],
'transactions': block['transactions'],
'proof': block['proof'],
'previous_hash': block['previous_hash'],
}
return jsonify(response), 200
去postman 依次请求chain（查看当前链）、transactions/new（新建交易，注意是post方法提交的json数据）、mine（打包区块）、chain
这时，一个单节点的区块链流程基本实现。
节点注册接口
# 节点注册接口
@app.route('/nodes/register', methods=['POST'])
def register_nodes():
values = request.get_json()
nodes = values.get('nodes')
if nodes is None:
return "Error: 请提供一个符合规则的节点", 400
for node in nodes:
blockchain.register_node(node)
response = {
'message': '新节点已经被添加！',
'total_nodes': list(blockchain.nodes),
}
return jsonify(response), 201
测试一下
共识接口
# 共识接口
@app.route('/nodes/resolve', methods=['GET'])
def consensus():
replaced = blockchain.resolve_conflicts()
if replaced:
response = {'message': '当前链不符合要求，已被替换', 'new_chain': blockchain.chain}
else:
response = {'message': '当前链符合要求', 'chain': blockchain.chain}
return jsonify(response), 200
完整运行
- 打开两个终端构造两个节点5000 和 5001
- 分别查看5000节点 和 5001节点 的当前链
5000节点
5001节点
均只有一个创世区块 - 接着对5000节点，建立新的交易，并封装区块，再次查看链，此时应该有链上应该有两个区块，而5001节点没有操作，所以链中只有一个块
- 此时将5001节点注册到5000节点中，5000节点注册到5001节点中，由于共识机制，选取最长的链，所以此时查看5001节点的链时，会出现两个节点而不是一个。
至此，简易区块链实现结束。
完整代码
import hashlib
import json
from time import time
from urllib.parse import urlparse # url解析
from uuid import uuid4 # 生成唯一id
from flask import Flask, jsonify, request
from typing import Any, Dict, List
import requests
from argparse import ArgumentParser # 命令行参数解析
class Blockchain:
def __init__(self):
self.chain = [] # 存块
self.current_transactions = [] # 交易实体
self.nodes = set() # 无重复的节点集合
# 创建创世区块
self.new_block(previous_hash='1', proof=100)
def register_node(self, address: str) -> None:
"""添加一个新节点到节点集中
Args:
address (str): 节点的地址。Eg："http://127.0.0.1:5002"
"""
parsed_url = urlparse(address) # 解析url参数
self.nodes.add(parsed_url.netloc) # 获取域名服务器
def new_block(self, proof: int, previous_hash=None): # 新建区块
block = {
'index': len(self.chain) + 1,
'timestamp': time(),
'transactions': self.current_transactions,
'proof': proof,
'previous_hash': previous_hash or self.hash(self.last_block),
}
self.current_transactions = [] # 新建区块打包后重置当前交易信息
self.chain.append(block) # 把新建的区块加入链
return block
def new_transaction(self, sender: str, recipient: str, amount: int) -> int:
"""添加新的交易
Args:
sender (str): 发送方
recipient (str): 接收方
amount (int): 金额
Returns:
int: 返回一个包含此交易的区块序号
"""
self.current_transactions.append({
'sender': sender,
'recipient': recipient,
'amount': amount
})
return self.last_block['index'] + 1
@staticmethod
def hash(block: Dict[str, Any]) -> str:
"""计算哈希值,返回哈希后的摘要信息
Args:
block (Dict[str, Any]): 传入一个块
Returns:
str: 摘要信息
"""
block_string = json.dumps(block, sort_keys=True).encode()
return hashlib.sha256(block_string).hexdigest()
@property
def last_block(self) -> Dict[str, Any]: # 获取当前链中最后一个区块
return self.chain[-1]
def proof_of_work(self, last_proof: int) -> int:
"""工作量计算，计算一个符合要求的哈希值
Args:
last_proof (int): 上一个块的工作量随机数
Returns:
int: 返回符合要求的工作量随机数
"""
proof = 0
while self.valid_proof(last_proof, proof) is False:
proof += 1
# print(proof) 输出计算结果
return proof
def vaild_chain(self, chain: List[Dict[str, Any]]) -> bool:
"""验证链是否合理：最长且有效
Args:
chain (List[Dict[str, Any]]): 传入链
Returns:
bool: 返回是否有效
"""
last_block = chain[0] # 从第一个创世区块开始遍历验证
current_index = 1
while current_index < len(chain):
block = chain[current_index]
print(f'{last_block}')
print(f'{block}')
print("\n-----------\n")
# 如果当前区块的前哈希和前一个计算出来的哈希值不同则是无效链
if block['previous_hash'] != self.hash(last_block):
return False
# 检验工作量证明是否符合要求
if not self.valid_proof(last_block['proof'], block['proof']):
return False
last_block = block
current_index += 1
return True
def valid_proof(self, last_proof: int, proof: int) -> bool:
"""工作量证明验证，验证计算结果是否以2个0开头
Args:
last_proof (int): 前工作证明
proof (int): 当前工作证明
Returns:
bool: 返回验证是否有效
"""
guess = f'{last_proof}{proof}'.encode()
guess_hash = hashlib.sha256(guess).hexdigest()
# print(guess_hash) 输出计算过程
if guess_hash[0:2] == "00":
return True
else:
return False
def resolve_conflicts(self) -> bool:
"""共识算法，解决冲突，以最长且有效的链为主
Returns:
bool: 冲突是否解决成功
"""
neighbours = self.nodes # 获取节点信息
new_chain = None # 定义可能的新链
max_length = len(self.chain) # 获取当前链长度
for node in neighbours: # 获取节点的链条信息，如果更长且有效则直接替换
response = requests.get(f'http://{node}/chain')
if response.status_code == 200:
length = response.json()['length']
chain = response.json()['chain']
if length > max_length and self.vaild_chain(chain):
max_length = length
new_chain = chain
if new_chain:
self.chain = new_chain
return True
return False
app = Flask(__name__) # flask框架
node_identifier = str(uuid4()).replace('-', '') # 使者获取一个唯一的uid
blockchain = Blockchain()
# 添加新建交易接口
@app.route('/transactions/new', methods=['POST'])
def new_transaction():
values = request.get_json()
required = ['sender', 'recipient', 'amount']
if not all(k in values for k in required):
return '确少参数', 400
index = blockchain.new_transaction(values['sender'], values['recipient'],
values['amount'])
response = {'message': f'交易将会被添加到块 {index}'}
return jsonify(response), 201
# 添加新建打包区块接口
@app.route('/mine', methods=['GET'])
def mine():
last_block = blockchain.last_block # 获取链上最后一个区块的信息
last_proof = last_block['proof']
proof = blockchain.proof_of_work(last_proof)
# 发送者为 "0" 表明是新挖出的币,为矿工提供奖励
blockchain.new_transaction(
sender="0",
recipient=node_identifier,
amount=1,
)
block = blockchain.new_block(proof, None) # 生成一个新块
response = {
'message': "打包成功，新区块已生成！",
'index': block['index'],
'transactions': block['transactions'],
'proof': block['proof'],
'previous_hash': block['previous_hash'],
}
return jsonify(response), 200
# 查看链接口
@app.route('/chain', methods=['GET'])
def full_chain():
response = {
'chain': blockchain.chain,
'length': len(blockchain.chain),
}
return jsonify(response), 200
# 节点注册接口
@app.route('/nodes/register', methods=['POST'])
def register_nodes():
values = request.get_json()
nodes = values.get('nodes')
if nodes is None:
return "Error: 请提供一个符合规则的节点", 400
for node in nodes:
blockchain.register_node(node)
response = {
'message': '新节点已经被添加！',
'total_nodes': list(blockchain.nodes),
}
return jsonify(response), 201
# 共识接口
@app.route('/nodes/resolve', methods=['GET'])
def consensus():
replaced = blockchain.resolve_conflicts()
if replaced:
response = {'message': '当前链不符合要求，已被替换', 'new_chain': blockchain.chain}
else:
response = {'message': '当前链符合要求', 'chain': blockchain.chain}
return jsonify(response), 200
if __name__ == "__main__":
parser = ArgumentParser() # 命令行参数解析，端口默认5000
parser.add_argument('-p',
'--port',
default=5000,
type=int,
help='port to listen on')
args = parser.parse_args()
port = args.port
app.run(host='127.0.0.1', port=port) # 启动web服务，默认本机