Blockchain.py

import hashlib
import datetime


class Block:
    def __init__(self, index, data, previousHash='00000'):
        self.index = index
        self.timestamp = str(datetime.datetime.now())
        self.data = data
        self.previousHash = previousHash
        self.hash = self.calculateHash()

    def calculateHash(self):
        return hashlib.sha256(str(self.index).encode('utf-8')
                              + self.previousHash.encode('utf-8')
                              + str(self.data).encode('utf-8')
                              + self.timestamp.encode('utf-8')).hexdigest()

    def isValid(self):
        return self.hash == self.calculateHash()

    def printBlock(self):
        return ("\nBlock #" + str(self.index)
                + "\nData: " + str(self.data)
                + "\nTimeStamp: " + str(self.timestamp)
                + "\nBlock Hash: " + str(self.hash)
                + "\nBlock Previous Hash: " + str(self.previousHash)
                + "\n---------------")


class BlockChain:
    def __init__(self, file="block.chain"):
        self.chain = [Block(0, "Genesis")]
        self.file = file

    def getLatestBlock(self):
        return self.chain[len(self.chain) - 1]

    def getNextIndex(self):
        return self.getLatestBlock().index + 1

    def generateBlock(self, data):
        self.chain.append(Block(self.getNextIndex(), data, self.getLatestBlock().hash))

    def validate(self):
        for i in range(1, len(self.chain)):
            if not self.chain[i].isValid():
                return False
            if self.chain[i].previousHash != self.chain[i - 1].hash:
                return False
        return True