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How to Build Blockchain using Python?

How to Build Blockchain using Python?

In this blog post, we will delve into the exciting realm of blockchain technology, its significance, and how it can be implemented using the versatile programming language Python. Whether you’re a beginner or an experienced developer, this comprehensive guide will equip you with the knowledge and skills to create your own blockchain network, foster transparency, and enhance security.

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Blockchain Basics

Before going into Python blockchain development, it’s critical to understand the core fundamentals of blockchain technology. A blockchain, at its heart, is a distributed ledger that is maintained by a network of nodes. Each node has its own copy of the ledger, and transactions are confirmed and added to it via a consensus mechanism.

One of the most significant advantages of blockchain is that it is immutable and tamper-proof. Once added to the blockchain, a block cannot be changed or removed, making it a safe way to store data and perform transactions. Blockchain also eliminates the need for intermediaries, as transactions may be carried out directly between parties without the involvement of a third party. Proof of Work (PoW), Proof of Stake (PoS), and practical Byzantine Fault Tolerance (pBFT) are three prevalent blockchain consensus algorithms.

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Creating a Blockchain Class

To create a basic blockchain class in Python, you can follow these steps.

  • Define a Block class that represents a block in the blockchain. Each block should have the following attributes.
    • index: the index of the block in the blockchain
    • data: any data that the block should store
    • timestamp: the timestamp of when the block was created
    • previous_hash: the hash of the previous block in the blockchain
    • hash: the hash of the current block  calculated later)
  • Define a Blockchain class that represents the blockchain itself. The class should have the following methods.
    • __init__(): initializes the blockchain with a genesis block
    • add_block(): adds a new block to the blockchain
    • calculate_hash(): calculates the hash of the current block (using the SHA-256 algorithm, for example)
    • get_latest_block(): returns the latest block in the blockchain
    • is_chain_valid(): checks if the blockchain is valid (i.e., all blocks are linked together correctly and their hashes are valid)
  • In the __init__() method of the Blockchain class, create the genesis block (i.e., the first block in the blockchain) with the following attributes.
    • index: 0
    • timestamp: the current time
    • data: any arbitrary data
    • previous_hash: None (since this is the first block)
    • hash: the hash of the genesis block calculated using the calculate_hash() method)
  • In the add_block() method of the Blockchain class, create a new block with the following attributes.
    • index: the index of the new block (which is the index of the latest block + 1)
    • timestamp: the current time
    • data: the data that the block should store
    • previous_hash: the hash of the latest block
    • hash: the hash of the new block (which can be calculated using the calculate_hash() method)
  • In the calculate_hash() method of the Blockchain class, calculate the hash of the current block by concatenating the block’s attributes (excluding the hash attribute) and using a hashing algorithm (such as SHA-256) to generate a hash value.
  • In the is_chain_valid() method of the Blockchain class, iterate through all blocks in the blockchain and check if their hashes are valid and if they are linked together correctly (i.e., each block’s previous_hash attribute should equal the hash of the previous block).

With these steps, you can create a basic blockchain class in Python programming language.

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How to Build a Blockchain in Python?

Steps to build a blockchain in Python:

  • Import the Necessary Libraries: To build a blockchain in Python, you will need to import the following libraries: 
    • hashlib for generating hashes
    • json for storing data in JSON format
    • random for generating random numbers
  • Define the Block Class: A block is a unit of data in the blockchain. It typically contains a
    • timestamp
    • A list of transactions
    • The hash of the previous block
    • nonce (a random number).
      You can define a Block class with these attributes and a method to calculate the block’s hash.
  • Define the Blockchain Class: We can define a Blockchain class that initializes the genesis block in its constructor and has a method to add new blocks to the chain. This Blockchain class creates a list of blocks linked together using their hashes. The first block created by the constructor becomes the genesis block. The add_block() method then appends subsequent blocks to this chain.
  • Create a Function to Mine a New Block: We can mine new blocks by creating a function that takes the previous block’s hash and a list of transactions as input. The function then finds a nonce that satisfies the blockchain’s difficulty requirements. With a valid nonce, the function returns a new block appended to the chain. Miners actively mine new blocks in this manner, adding them to the blockchain.
  • Create a function to Validate the Blockchain: To maintain the blockchain’s integrity, you must confirm that each block’s hash is right and that the blocks are correctly connected. You can write a function that loops across the chain and validates these attributes.
  • Create a Main Function: The primary role will be to create the blockchain, mine for a few additional blocks, and then validate the blockchain. This function checks the accuracy and functionality of your implementation.

Here is an example of a simple blockchain in Python:

import hashlib
import json
import random
class Block:
    def __init__(self, timestamp, transactions, previous_hash):
        self.timestamp = timestamp
        self.transactions = transactions
        self.previous_hash = previous_hash
        self.nonce = random.randint(0, 1000000)
    def hash(self):
        return hashlib.sha256(
class Blockchain:
    def __init__(self):
        self.chain = [Block(0, [], '0')]
    def create_block(self, transactions):
        previous_hash = self.chain[-1].hash()
        new_block = Block(
            int(time.time()), transactions, previous_hash
        while not new_block.hash().startswith('0000'):
            new_block.nonce += 1
        return new_block
    def mine_block(self):
        new_block = self.create_block([])
        while not self.validate_block(new_block):
            new_block.nonce += 1
        return new_block
    def validate_block(self, block):
        return block.hash().startswith('0000')
def main():
    blockchain = Blockchain()
    block = blockchain.create_block([])
if __name

Get started on building your own Python blockchain tutorial with our step-by-step blockchain tutorial!

Building a Blockchain Network

Building a Blockchain Network

Building a blockchain network involves creating a decentralized system that allows multiple nodes to communicate and reach a consensus on the state of the blockchain. The network must be secure, reliable, and resistant to attacks and malicious behavior. To build a blockchain network, you need to

  • Design the blockchain itself – This includes defining the block’s data format, the chosen consensus algorithm, and the guidelines for validating and verifying transactions.
  • Develop the software for the nodes – As well as any software tools required for network monitoring and management, you will need to design and implement the software for the nodes that will run the blockchain.
  • Set up the network – You can start establishing the network once the blockchain is defined and the software is created. You must deploy the nodes necessary to run the blockchain and set them up so they can connect with one another. The network may also need security measures put in place to guard against assaults and other harmful activity.
  • Test the network – In order to make sure that the network is operating correctly and that all nodes can interact and come to an agreement over the status of the blockchain, you must lastly test the network.

The process of creating a blockchain network is intricate and demands careful planning, design, and execution. However, it is feasible to build a safe and trustworthy blockchain network that can be used for a variety of applications, from financial transactions to supply chain management and beyond, with the correct tools and knowledge.

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Implementing a Blockchain Application

Implementation of a blockchain application involves using blockchain technology to solve real-world problems in a secure and efficient way. The process of implementing a blockchain application can be broken down into the following steps:

  • Identify the problem to be solved – Finding the issue that the application will address is the first step in putting a blockchain application into practice. This could involve anything from enhancing the effectiveness of financial transactions to tracing the provenance of commodities in a supply chain.
  • Choose the appropriate blockchain platform – After the issue has been located, you must decide which blockchain platform is best for your application. There are numerous blockchain platforms available, each with unique advantages and disadvantages.
  • Develop the smart contract – The brains of a blockchain application are smart contracts. It is a self-executing contract that includes the application’s logic and rules. Employing a programming language like Solidity, you must create a smart contract.
  • Test the smart contract – The constructed smart contract must undergo extensive testing to make sure it is operating as planned. This will entail evaluating the contract’s functioning and testing it for errors and vulnerabilities.
  • Deploy the smart contract – It is possible to deploy the smart contract on the blockchain platform once it has been through testing and is ready to use.
  • Build the user interface – Building the user interface for your blockchain application is the last step. Depending on the requirements of your consumers, this might be a desktop application, a mobile application, or both.

A thorough understanding of blockchain technology, as well as programming and software development know-how, are required to implement a blockchain application. However, with the right tools and expertise, it is possible to build secure, efficient, and scalable blockchain applications that can be used to solve a wide range of real-world problems.

Python Blockchain Projects

Some Python-based blockchain projects that you can explore:

  • Blockchain Implementation: Create your own basic blockchain from scratch in Python, complete with blocks, hashing, and proof-of-work.
  • Cryptocurrency: Develop a simple cryptocurrency (bitcoin) using blockchain technology with features like wallet creation, transaction processing, and balance management.
  • Decentralized Voting System: Build a secure and transparent voting system using blockchain to ensure the integrity of votes and prevent tampering.
  • Supply Chain Management: Implement a supply chain management system on the blockchain to track and verify the provenance of products at each stage of the supply chain.
  • Blockchain-Based File Storage: Create a decentralized file storage system where users can upload and retrieve files securely using blockchain.
  • Smart Contracts: Explore smart contracts using a blockchain platform like Ethereum to automate contractual agreements and processes.
  • Decentralized Finance (DeFi) Application: Create a DeFi application, such as a decentralized exchange (DEX) or lending platform, utilizing smart contracts and blockchain.
  • Tokenization Platform: Design a platform that allows users to create and manage their custom tokens on the blockchain.

Remember that blockchain projects can be intricate, so it’s beneficial to understand how blockchain technology works before diving into these projects. Additionally, always be cautious with security considerations and thoroughly test your implementations.


Finally, creating a blockchain with Python is a difficult but worthwhile effort. You may build a decentralized, secure application that is also transparent and impenetrable by using the procedures listed below. Python is a great option for deploying blockchain technology because of its adaptability and simplicity. Learning how to create a blockchain using Python is a useful ability that can provide new chances in the technology sector given the rising demand for blockchain engineers.

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About the Author

Senior Reserch Analyst - Cloud Computing

Arpit has years of experience working with top-tier tech companies and has developed a plethora of knowledge in Data Analysis and Machine Learning. He currently holds the position of Senior Research Analyst in Cloud Computing. His passion for writing extends beyond the technical world, crafting profound narratives that bridge the gap between complex concepts and accessible understanding.