blockchain.py

import hashlib as hasher
import datetime as date

class Block:
	def __init__(self, index, timestamp, data, previous_hash):
		self.index = index
		self.timestamp = timestamp
		self.data = data
		self.previous_hash = previous_hash
		self.hash = self.hash_block()

	def hash_block(self):
		sha = hasher.sha256()
		sha.update(
			str(self.index) + 
			str(self.timestamp) +
			str(self.data) +
			str(self.previous_hash))
		return sha.hexdigest()

# Genesis block
def create_genesis_block():
	# This manually constructs the block with
	# Index of zero and arbitrary previous hash
	return Block(0, date.datetime.now(), "Genesis Block", "0")

def next_block(last_block):
	this_index = last_block.index + 1
	this_timestamp = date.datetime.now()
	this_data = "Hey!, I'm block" + str(this_index)
	this_hash = last_block.hash
	return Block(this_index, this_timestamp, this_data, this_hash)

# Create the blockchain and add the genesis block
blockchain = [create_genesis_block()]
previous_block = blockchain[0]

# Adding blocks
num_of_blocks_to_add = 20

# Add blocks to the chain
for i in range(0, num_of_blocks_to_add):
	block_to_add = next_block(previous_block)
	blockchain.append(block_to_add)
	previous_block = block_to_add
	# Snitch about it now!
	print ("Block #{} has been added to the blockchain!".format(block_to_add.index))
	print ("Hash: {}\n".format(block_to_add.hash))