barebones blockchain example

blockchain.py

import hashlib
import time


class Block:
    def __init__(self, data, previous_hash=None):
        self.data = data
        self.previous_hash = previous_hash
        self.nonce = 0
        self.hash = self.calculate_hash()

    def calculate_hash(self):
        data = str(self.data) + str(self.previous_hash) + str(self.nonce)
        return hashlib.sha256(data.encode()).hexdigest()

    def mine_block(self, difficulty):
        start_time = time.time()
        while self.hash[0:difficulty] != "0" * difficulty:
            self.hash = self.calculate_hash()
            print(f"Mining... {self.nonce=:,} {self.hash=}")
            self.nonce += 1
        print(f"Block mined in {int(self.nonce / (time.time() - start_time)):,} H/s")

    def __repr__(self):
        return f"{self.__class__.__name__}({self.previous_hash=}, {self.nonce=:,}, {self.data=})"


class Blockchain(list):
    def __init__(self):
        super().__init__([Block("Genesis Block", "0")])

    def add_block(self, new_block, difficulty=4):
        new_block.previous_hash = self[-1].hash
        new_block.mine_block(difficulty)
        self.append(new_block)


if __name__ == "__main__":
    blockchain = Blockchain()
    blockchain.add_block(Block(["Create 2,171,879,003 coins"]))
    print("\033[92m", *blockchain, "\033[0m", sep="\n")