Simple Text Data Block Chain Implementation

import hashlib
import datetime

class Block:
    def __init__(self, index: int, timestamp: datetime.datetime, data: str, previous_hash: str):
        self.index = index
        self.timestamp = timestamp
        self.data = data
        self.previous_hash = previous_hash
        self.hash = self.calculate_hash()

    def calculate_hash(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()

class Blockchain:
    def __init__(self):
        self.chain = [self.create_genesis_block()]

    def create_genesis_block(self) -> Block:
        return Block(0, datetime.datetime.now(), "Genesis Block", "0")

    def get_latest_block(self) -> Block:
        return self.chain[-1]

    def add_block(self, new_block: Block):
        new_block.previous_hash = self.get_latest_block().hash
        new_block.hash = new_block.calculate_hash()
        self.chain.append(new_block)

    def is_chain_valid(self) -> bool:
        for i in range(1, len(self.chain)):
            current_block = self.chain[i]
            previous_block = self.chain[i - 1]
            if current_block.hash != current_block.calculate_hash():
                return False
            if current_block.previous_hash != previous_block.hash:
                return False
        return True

    def print_blockchain(self):
        for block in blockchain.chain:
            print("Index:", block.index)
            print("Timestamp:", block.timestamp)
            print("Data:", block.data)
            print("Previous Hash:", block.previous_hash)
            print("Current Hash:", block.hash)
            print()


# Example usage
blockchain = Blockchain()
blockchain.add_block(Block(1, datetime.datetime.now(), "Data 1", ""))
blockchain.add_block(Block(2, datetime.datetime.now(), "Data 2", ""))
blockchain.add_block(Block(3, datetime.datetime.now(), "Data 3", ""))
blockchain.add_block(Block(4, datetime.datetime.now(), "Data 4", ""))

# Print blockchain
blockchain.print_blockchain()

print("Blockchain is valid:", blockchain.is_chain_valid())

# Modify data to demonstrate tampering
blockchain.chain[2].data = "Tampered Data"
print("Blockchain is valid after tampering:", blockchain.is_chain_valid())