blockchain.py

from block import Block
from datetime import datetime


class Blockchain(object):
	def __init__(self):
		super().__init__()
		self.chain = [Block(0, datetime.now().timestamp(), 'Genesis Block', '0')]

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

	def is_valid(self, block):
		current_block = self.chain[len(self.chain) - 1]

		if current_block.index + 1 != block.index:
			return False
		elif block.previous_hash != current_block.hash:
			return False
		elif block.hash != block.calculate_hash():
			return False

		return True

	def add_block(self, data):
		timestamp = datetime.now().timestamp()
		index = len(self.chain)
		previous_hash = self.get_previous_hash()
		new_block = Block(index, timestamp, data, previous_hash)

		if self.is_valid(new_block):
			self.chain.append(new_block)
		else:
			print('ERROR: Block is invalid!')

	def print_blockchain(self):
		print()
		for block in self.chain:
			print('{}  {}'.format(block.index, block.real_time()))
			print(block.data)
			print(block.hash)
			print()