使用Python 搭建自己的区块链

 pip install Flask==0.12.2 requests==2.18.4

class Blockchain(object):
 def __init__(self):
 self.chain = []
 self.current_transactions = []

 def new_block(self):
 # Creates a new Block and adds it to the chain
 pass

 def new_transaction(self):
 # Adds a new transaction to the list of transactions
 pass

 @staticmethod
 def hash(block):
 # Hashes a Block
 pass

 @property
 def last_block(self):
 # Returns the last Block in the chain
 pass

block = {
 'index': 1,
 'timestamp': 1506057125.900785,
 'transactions': [
 {
 'sender': "8527147fe1f5426f9dd545de4b27ee00",
 'recipient': "a77f5cdfa2934df3954a5c7c7da5df1f",
 'amount': 5,
 }
 ],
 'proof': 324984774000,
 'previous_hash': "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824"
}

class Blockchain(object):
 ...

 def new_transaction(self, sender, recipient, amount):
 """
 Creates a new transaction to go into the next mined Block
 :param sender: <str> Address of the Sender
 :param recipient: <str> Address of the Recipient
 :param amount: <int> Amount
 :return: <int> The index of the Block that will hold this transaction
 """

 self.current_transactions.append({
 'sender': sender,
 'recipient': recipient,
 'amount': amount,
 })

 return self.last_block['index'] + 1

import hashlib
import json
from time import time

class Blockchain(object):
 def __init__(self):
 self.current_transactions = []
 self.chain = []

 # 创建创世区块
 self.new_block(previous_hash=1, proof=100)

 def new_block(self, proof, previous_hash=None):
 """
 创建一个新的区块到区块链中
 :param proof: <int> 由工作证明算法生成的证明
 :param previous_hash: (Optional) <str> 前一个区块的 hash 值
 :return: <dict> 新区块
 """

 block = {
 'index': len(self.chain) + 1,
 'timestamp': time(),
 'transactions': self.current_transactions,
 'proof': proof,
 'previous_hash': previous_hash or self.hash(self.chain[-1]),
 }

 # 重置当前交易记录
 self.current_transactions = []

 self.chain.append(block)
 return block

 def new_transaction(self, sender, recipient, amount):
 """
 创建一笔新的交易到下一个被挖掘的区块中
 :param sender: <str> 发送人的地址
 :param recipient: <str> 接收人的地址
 :param amount: <int> 金额
 :return: <int> 持有本次交易的区块索引
 """
 self.current_transactions.append({
 'sender': sender,
 'recipient': recipient,
 'amount': amount,
 })

 return self.last_block['index'] + 1

 @property
 def last_block(self):
 return self.chain[-1]

 @staticmethod
 def hash(block):
 """
 给一个区块生成 SHA-256 值
 :param block: <dict> Block
 :return: <str>
 """

 # 我们必须确保这个字典（区块）是经过排序的，否则我们将会得到不一致的散列
 block_string = json.dumps(block, sort_keys=True).encode()
 return hashlib.sha256(block_string).hexdigest()

from hashlib import sha256
x = 5
y = 0 # We don't know what y should be yet...
while sha256(f'{x*y}'.encode()).hexdigest()[-1] != "0":
 y += 1
print(f'The solution is y = {y}')

hash(5 * 21) = 1253e9373e...5e3600155e860

import hashlib
import json

from time import time
from uuid import uuid4

class Blockchain(object):
 ...

 def proof_of_work(self, last_proof):
 """
 Simple Proof of Work Algorithm:
 - Find a number p' such that hash(pp') contains leading 4 zeroes, where p is the previous p'
 - p is the previous proof, and p' is the new proof
 :param last_proof: <int>
 :return: <int>
 """

 proof = 0
 while self.valid_proof(last_proof, proof) is False:
 proof += 1

 return proof

 @staticmethod
 def valid_proof(last_proof, proof):
 """
 Validates the Proof: Does hash(last_proof, proof) contain 4 leading zeroes?
 :param last_proof: <int> Previous Proof
 :param proof: <int> Current Proof
 :return: <bool> True if correct, False if not.
 """

 guess = f'{last_proof}{proof}'.encode()
 guess_hash = hashlib.sha256(guess).hexdigest()
 return guess_hash[:4] == "0000"

import hashlib
import json
from textwrap import dedent
from time import time
from uuid import uuid4

from flask import Flask

class Blockchain(object):
 ...

# Instantiate our Node（实例化我们的节点）
app = Flask(__name__)

# Generate a globally unique address for this node（为这个节点生成一个全球唯一的地址）
node_identifier = str(uuid4()).replace('-', '')

# Instantiate the Blockchain（实例化 Blockchain类）
blockchain = Blockchain()

@app.route('/mine', methods=['GET'])
def mine():
 return "We'll mine a new Block"

@app.route('/transactions/new', methods=['POST'])
def new_transaction():
 return "We'll add a new transaction"

@app.route('/chain', methods=['GET'])
def full_chain():
 response = {
 'chain': blockchain.chain,
 'length': len(blockchain.chain),
 }
 return jsonify(response), 200

if __name__ == '__main__':
 app.run(host='0.0.0.0', port=5000)

{
 "sender": "my address",
 "recipient": "someone else's address",
 "amount": 5
}

import hashlib
import json
from textwrap import dedent
from time import time
from uuid import uuid4

from flask import Flask, jsonify, request

...

@app.route('/transactions/new', methods=['POST'])
def new_transaction():
 values = request.get_json()

 # Check that the required fields are in the POST'ed data
 required = ['sender', 'recipient', 'amount']
 if not all(k in values for k in required):
 return 'Missing values', 400

 # Create a new Transaction
 index = blockchain.new_transaction(values['sender'], values['recipient'], values['amount'])

 response = {'message': f'Transaction will be added to Block {index}'}
 return jsonify(response), 201

import hashlib
import json

from time import time
from uuid import uuid4

from flask import Flask, jsonify, request

...

@app.route('/mine', methods=['GET'])
def mine():
 # We run the proof of work algorithm to get the next proof...
 last_block = blockchain.last_block
 last_proof = last_block['proof']
 proof = blockchain.proof_of_work(last_proof)

 # We must receive a reward for finding the proof.
 # The sender is "0" to signify that this node has mined a new coin.
 blockchain.new_transaction(
 sender="0",
 recipient=node_identifier,
 amount=1,
 )

 # Forge the new Block by adding it to the chain
 previous_hash = blockchain.hash(last_block)
 block = blockchain.new_block(proof, previous_hash)

 response = {
 'message': "New Block Forged",
 'index': block['index'],
 'transactions': block['transactions'],
 'proof': block['proof'],
 'previous_hash': block['previous_hash'],
 }
 return jsonify(response), 200

$ python blockchain.py
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

$ curl -X POST -H "Content-Type: application/json" -d '{
 "sender": "d4ee26eee15148ee92c6cd394edd974e",
 "recipient": "someone-other-address",
 "amount": 5
}' "http://localhost:5000/transactions/new"

{
 "chain": [
 {
 "index": 1,
 "previous_hash": 1,
 "proof": 100,
 "timestamp": 1506280650.770839,
 "transactions": []
 },
 {
 "index": 2,
 "previous_hash": "c099bc...bfb7",
 "proof": 35293,
 "timestamp": 1506280664.717925,
 "transactions": [
 {
 "amount": 1,
 "recipient": "8bbcb347e0634905b0cac7955bae152b",
 "sender": "0"
 }
 ]
 },
 {
 "index": 3,
 "previous_hash": "eff91a...10f2",
 "proof": 35089,
 "timestamp": 1506280666.1086972,
 "transactions": [
 {
 "amount": 1,
 "recipient": "8bbcb347e0634905b0cac7955bae152b",
 "sender": "0"
 }
 ]
 }
 ],
 "length": 3
}

...
from urllib.parse import urlparse
...

class Blockchain(object):
 def __init__(self):
 ...
 self.nodes = set()
 ...

 def register_node(self, address):
 """
 Add a new node to the list of nodes
 :param address: <str> Address of node. Eg. 'http://192.168.0.5:5000'
 :return: None
 """

 parsed_url = urlparse(address)
 self.nodes.add(parsed_url.netloc)

...
import requests

class Blockchain(object)
 ...

 def valid_chain(self, chain):
 """
 Determine if a given blockchain is valid
 :param chain: <list> A blockchain
 :return: <bool> True if valid, False if not
 """

 last_block = chain[0]
 current_index = 1

 while current_index < len(chain):
 block = chain[current_index]
 print(f'{last_block}')
 print(f'{block}')
 print("
-----------
")
 # Check that the hash of the block is correct
 if block['previous_hash'] != self.hash(last_block):
 return False

 # Check that the Proof of Work is correct
 if not self.valid_proof(last_block['proof'], block['proof']):
 return False

 last_block = block
 current_index += 1

 return True

 def resolve_conflicts(self):
 """
 This is our Consensus Algorithm, it resolves conflicts
 by replacing our chain with the longest one in the network.
 :return: <bool> True if our chain was replaced, False if not
 """

 neighbours = self.nodes
 new_chain = None

 # We're only looking for chains longer than ours
 max_length = len(self.chain)

 # Grab and verify the chains from all the nodes in our network
 for node in neighbours:
 response = requests.get(f'http://{node}/chain')

 if response.status_code == 200:
 length = response.json()['length']
 chain = response.json()['chain']

 # Check if the length is longer and the chain is valid
 if length > max_length and self.valid_chain(chain):
 max_length = length
 new_chain = chain

 # Replace our chain if we discovered a new, valid chain longer than ours
 if new_chain:
 self.chain = new_chain
 return True

 return False

@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), 200