input: Write a function to build a simple blockchain system in Python by implementing the Block class and the necessary functions to create, add, and print blocks. The function should include the Block class definition, the create_blockchain function, and the print_blockchain function. The function should also handle a list of transactions for adding to the blockchain.
  
  
  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_transactions):
      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(blockchain):
      for block in blockchain:
          block_index = str(block.index)
          block_timestamp = str(block.timestamp)
          block_data = str(block.data)
          block_hash = block.hash
          print("Block #" + block_index + " " + block_timestamp + " " + block_data + " " + block_hash)
  
  assert create_blockchain([{"transaction1"}, {"transaction2"}])==True
  assert print_blockchain(blockchain)==True
  assert len(blockchain)==2
  assert blockchain[0].index==0
  assert blockchain[1].previous_hash==blockchain[0].hash
  
output: 
  import hashlib
  import json
  from time import time
  
  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 = hashlib.sha256()
          sha.update((str(self.index) + 
                      str(self.timestamp) + 
                      str(self.data) + 
                      str(self.previous_hash)).encode('utf-8'))
          return sha.hexdigest()
  
  def create_genesis_block():
      return Block(0, time(), "Genesis Block", "0")
  
  def next_block(last_block, data):
      this_index = last_block.index + 1
      this_timestamp = time()
      this_data = data
      this_hash = last_block.hash
      return Block(this_index, this_timestamp, this_data, this_hash)
  
  def create_blockchain(blockchain_transactions):
      blockchain = [create_genesis_block()]
      previous_block = blockchain[0]
  
      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
      return blockchain
  
  def print_blockchain(blockchain):
      for block in blockchain:
          block_index = str(block.index)
          block_timestamp = str(block.timestamp)
          block_data = str(block.data)
          block_hash = block.hash
          print("Block #" + block_index + " " + block_timestamp + " " + block_data + " " + block_hash)
  