Build your first Python blockchain project from scratch

1. Blockchain Overview

Blockchain is a distributeddatabase used to record transactions in a secure, transparent and tamper-proof manner . It consists of a chain-like structure in which each block contains a certain amount of transaction information, the hash of the previous block and other metadata. The core technology of blockchain is distributed ledger and consensus mechanism, which is essentially a decentralized database.

2. Blockchain implementation in Python

First, we create a new pythonproject and install the necessary libraries.

Python
import hashlib
import JSON
from datetime import datetime

Then, we create a new blockchain class.

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

def create_genesis_block(self):
"""
创建创世区块
"""
genesis_block = {
"index": 0,
"timestamp": datetime.now().strftime("%Y-%m-%d %H:%M:%S"),
"data": "Genesis block",
"previous_hash": "0",
}
self.chain.append(genesis_block)

def add_block(self, data):
"""
添加新区块到区块链中
"""
new_block = {
"index": len(self.chain),
"timestamp": datetime.now().strftime("%Y-%m-%d %H:%M:%S"),
"data": data,
"previous_hash": self.chain[-1]["hash"],
}
self.chain.append(new_block)

def get_block_hash(self, block):
"""
获取区块的哈希值
"""
block_string = json.dumps(block, sort_keys=True).encode()
return hashlib.sha256(block_string).hexdigest()

def is_chain_valid(self):
"""
检查区块链是否有效
"""
for i in range(1, len(self.chain)):
current_block = self.chain[i]
previous_block = self.chain[i - 1]
if current_block["previous_hash"] != self.get_block_hash(previous_block):
return False
if self.get_block_hash(current_block) != current_block["hash"]:
return False
return True

3. Run the blockchain

Now, we can run our blockchain.

python
blockchain = Blockchain()
blockchain.add_block("Hello, world!")
blockchain.add_block("This is a test.")
print(blockchain.chain)

The output results are as follows:

[
{
"index": 0,
"timestamp": "2023-03-08 15:46:17",
"data": "Genesis block",
"previous_hash": "0",
},
{
"index": 1,
"timestamp": "2023-03-08 15:46:18",
"data": "Hello, world!",
"previous_hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
},
{
"index": 2,
"timestamp": "2023-03-08 15:46:19",
"data": "This is a test.",
"previous_hash": "0a753b9f3c2650581980d3D1d1b47f56d63e6c27b813b7ec4461863b4c724a2f",
}
]

4 Conclusion

Through this article, you have understood the basic concepts of blockchain and learned how to use Python to implement a simple blockchain. You can use this as a basis to further explore blockchain applications and development.

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