title: How does this line " return self.last_block['index'] + 1 " works?
body: <p>I'm learning to create a blockchain system and cannot understand how this line fits into this code.
  Why and how last_block() is used with 'index'?</p>
  
  <p>class Blockchain(object):
      def <strong>init</strong>(self):
          self.chain = []
          self.current_transactions = []</p>
  
  <pre><code>def new_block(self):
      pass
  
  def new_transaction(self):
      pass
  
  @staticmethod
  def hash(block):
      pass
  
  @property
  def last_block(self):
      pass
  </code></pre>
  
  <p>block = {
      'index': 1,
      'timestamp': 1506057125.900785,
      'transactions': [
          {
              'sender': "8527147fe1f5426f9dd545de4b27ee00",
              'recipient': "a77f5cdfa2934df3954a5c7c7da5df1f",
              'amount': 5,
          }
      ],
      'proof': 324984774000,
      'previous_hash': "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824"
  }</p>
  
  <p>def new_transaction(self,sender,recipient,amount):
      self.current_transactions.append({
        'sender' : sender,
          'recipient':recipient,
          'amount':amount
      })</p>
  
  <pre><code>return self.last_block['index']+1
  </code></pre>