python 区块链程序

import hashlib
import json
from time import time
from uuid import uuid4
from flask import Flask, jsonify, request
from urllib.parse import urlparse
import requestsclass Blockchain(object):
def __init__(self):
self.chain = []
self.current_transactions = []
self.new_block(previous_hash=1, proof=None)
self.nodes = set() def register_node(self, address):
parsed_url = urlparse(address)
self.nodes.add(parsed_url.netloc) def valid_chain(self, chain):
last_block = chain[0]
current_index = 1
while current_index < len(chain):
block = chain[current_index]
print(f'{last_block}')
print(f'{block}')
print('\n---------------\n')
if block['previous_hash'] != self.hash(last_block):
return False
if not self.valid_proof(last_block['proof'], block['proof']):
return False
last_block = block
current_index += 1
return True def resolve_conflicts(self):
neighbours = self.nodes
new_chain = None
max_length = len(self.chain)
for node in neighbours:
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.valid_chain(chain):
max_length = length
new_chain = chain
if new_chain:
self.chain = new_chain
return True
return False def new_block(self, proof, previous_hash=None):
block = {
'index': len(self.chain) + 1,
'timestamp': time(),
'transactions': self.current_transactions,
'proof': proof,
'previous_hash': previous_hash or self.hash(self.chain[-1])
}
self.current_transactions = []
self.chain.append(block)
return block def new_transaction(self, sender, recipient, amount):
self.current_transactions.append({
'sender': sender,
'recipient': recipient,
'amount': amount
})
return self.last_block['index'] + 1 @staticmethod
def hash(block):
block_string = json.dumps(block, sort_keys=True).encode()
return hashlib.sha256(block_string).hexdigest() @property
def last_block(self):
return self.chain[-1] def proof_of_work(self, last_proof):
proof = 0
while self.valid_proof(last_proof, proof) is False:
proof += 1
return proof @staticmethod
def valid_proof(last_proof, proof):
guess = f'{last_proof}{proof}'.encode()
guess_hash = hashlib.sha256(guess).hexdigest()
return guess_hash[:4] == ""app = Flask(__name__)
node_identifier = str(uuid4()).replace('-', '')
blockchain = Blockchain()@app.route('/mine', methods=['GET'])
def mine():
last_block = blockchain.last_block
last_proof = last_block['proof']
proof = blockchain.proof_of_work(last_proof)
blockchain.new_transaction(
sender="",
recipient=node_identifier,
amount=1
)
block = blockchain.new_block(proof)
response = {
'message': "New Block Forged",
'index': block['index'],
'transactions': block['transactions'],
'proof': block['proof'],
'previous_hash': block['previous_hash']
}
return jsonify(response), 200@app.route('/transactions/new', methods=['POST'])
def new_transactions():
values = request.get_json()
print('*' * 20, values)
required = ['sender', 'recipient', 'amount']
if not all(k in values for k in required):
return "Missing Values", 400
index = blockchain.new_transaction(values['sender'], values['recipient'], values['amount'])
response = {'message': f'Transaction will be added to Block{index}'}
return jsonify(response), 201@app.route('/chain', methods=['GET'])
def full_chain():
response = {
'chain': blockchain.chain,
'length': len(blockchain.chain)
}
return jsonify(response), 200@app.route('/nodes/register', methods=['POST'])
def register_nodes():
values = request.get_json()
nodes = values.get('nodes')
if nodes is None:
return "Error: Please supply a valid list of nodes", 400
for node in nodes:
blockchain.register_node(node)
response = {
'message': 'New nodes have been added',
'total_nodes': list(blockchain.nodes)
}
return jsonify(response), 201@app.route('/nodes/resolve', methods=['GET'])
def consensus():
replaced = blockchain.resolve_conflicts()
if replaced:
response = {
'message': 'Our chain was replaced',
'new_chain': blockchain.chain
}
else:
response = {
'message': 'Our chain is authoritative',
'chain': blockchain.chain
}
return jsonify(response), 200if __name__ == '__main__':
app.run('0.0.0.0', port=5001)