FAQ: Build your own Mini-Blockchain! - Adding Blocks to the Blockchain

This community-built FAQ covers the “Adding Blocks to the Blockchain” exercise from the lesson “Build your own Mini-Blockchain!”.

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This exercise can be found in the following Codecademy content:

Introduction to Blockchain

FAQs on the exercise Adding Blocks to the Blockchain

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In the following code to add a new block:

def add_block(self, transactions):
    new_block=Block(transactions,self.chain[len(self.chain)-1].hash)
    self.chain.append(new_block)

firstly, where does the “transactions” come from and secondly, why aren’t we using self.transactions in the second line?

Up until this point we’ve been using sha256(string1.encode()) to hash something.

I don’t understand why we suddenly switch to .hash() and what it does.

chain is a list of dictionaries. The .hash is to call the value associated with the hash key in the dictionary located at len(self.chain)-1 in the list chain. The .hash is not acting as a method or function, simply as a dictionary key. Hopefully that helps.