input: import hashlib
  import json
  
  # Define the Block class
  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()
  
      # Create the hash of the block contents
      def hash_block(self):
          sha = hashlib.sha256()
          sha.update((str(self.index) + 
                      str(self.timestamp) + 
                      str(self.data) + 
                      str(self.previous_hash)).encode('utf-8'))
          return sha.hexdigest()
  
  # Create the blockchain
  def create_blockchain():
      blockchain = [create_genesis_block()]
      previous_block = blockchain[0]
  
      # Add blocks for each item in the list of transactions
      for i in range(1, len(blockchain_transactions)):
          block_to_add = next_block(previous_block, blockchain_transactions[i])
          blockchain.append(block_to_add)
          previous_block = block_to_add
  
  # Print the blockchain
  def print_blockchain():
      for block in blockchain:
          block_index = str(block.index)
          block_timestamp = str(block.timestamp)
          block_data = str(block.data)
          block_hash = block.hash
  
  # >>> create_blockchain()
  # >>> print_blockchain()
  
  # Expected output:
  # 0, <timestamp>, Genesis Block, <hash>
  # 1, <timestamp>, <data1>, <hash>
  # 2, <timestamp>, <data2>, <hash>
output:     print(f"{block_index}, {block_timestamp}, {block_data}, {block_hash}")
  
  # Create the genesis block
  def create_genesis_block():
      return Block(0, "01/01/2023", "Genesis Block", "0")
  
  # Generate the next block
  def next_block(last_block, data):
      this_index = last_block.index + 1
      this_timestamp = "01/01/2023"
      this_data = data
      this_hash = last_block.hash
      return Block(this_index, this_timestamp, this_data, this_hash)
  
  # List of transactions to be added to the blockchain
  blockchain_transactions = ["data1", "data2", "data3"]