minicoin.py

import hashlib as hasher
import datetime as date

# Define what a minicoin block is
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).encode('utf-8') + 
            str(self.timestamp).encode('utf-8') +
            str(self.data).encode('utf-8') + 
            str(self.previous_hash).encode('utf-8'))
        return sha.hexdigest()

# Generate genesis block
def create_genesis_block():
    # Manually construct a block with
    # index zero and arbitrary previous hash.
    return Block(0, date.datetime.now(), "Genesis Block", "0")

# Generate all later blocks in the blockchain
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]

# How many block shoud we add to the chain
# after the genesis block
num_of_block_to_add = 20

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