2.2 实现区块类结构，实现交易方法

"""
create by gaowenfeng on 2018/8/25
"""
import hashlib
import json

__author__ = "gaowenfeng"

from time import time

"""
区块的结构
{
"index": 0, 索引
"timestamp": "", 时间戳
"transactions": [
{
"sender": "",
"recipient": "",
"amount": 5
}
],
"proof": "", # 工作量证明
"previous_hash": "" # 上一个区块的hash
}
"""


class Blockchain:

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

# 创始区块 工作量证明随意，上一个区块hash值随意
self.new_block(proof=100, previous_hash=1)

def new_block(self, proof, previous_hash=None):

block = {
'index': len(self.chain) + 1, # 链的长度+1
'timestamp': time(),
'transactions': self.current_transactions,
'proof': proof,
'previous_hash': previous_hash or self.hash(self.last_block)
}

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
})

# 返回上一个区块的索引
return self.last_block['index']+1

@staticmethod
def hash(block):

block_string = json.dumps(block, sort_keys=True)

# hexdigest 是hash过后的摘要信息
return hashlib.sha256(block_string).hexdigest

@property
def last_block(self):
return self.chain(-1) # -1 数组里的最后一个元素