想学习区块链？那就用 Python 构建一个 | Linux 中国(2)

   @property [好文分享：www.11jj.com]

   def last_block(self):

       return self.chain[-1]

   @staticmethod

   def hash(block):

       """

       Creates a SHA-256 hash of a Block

       :param block: <dict> Block

       :return: <str>

       """

       # We must make sure that the Dictionary is Ordered, or we"ll have inconsistent hashes

       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

app = Flask(__name__)

# Generate a globally unique address for this node

node_identifier = str(uuid4()).replace("-", "")

# Instantiate the Blockchain

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