Python 區塊鏈與Web3開發指南

https://www.python.org/static/community_logos/python-logo-master-v3-TM.png

區塊鏈基礎概念

區塊鏈核心特性

python

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class Block:def __init__(self, index, timestamp, data, previous_hash):self.index = indexself.timestamp = timestampself.data = dataself.previous_hash = previous_hashself.hash = self.calculate_hash()def calculate_hash(self):import hashlibsha = hashlib.sha256()sha.update(f"{self.index}{self.timestamp}{self.data}{self.previous_hash}".encode('utf-8'))return sha.hexdigest()# 創建創世區塊
genesis_block = Block(0, "2023-01-01", "Genesis Block", "0")
print(f"創世區塊哈希: {genesis_block.hash}")

https://www.researchgate.net/publication/336707000/figure/fig1/AS:817393838129153@1572173939816/The-structure-of-a-blockchain-The-blockchain-is-a-linked-list-containing-blocks-of-data.png

Web3.py 入門

連接以太坊網絡

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from web3 import Web3# 連接Infura節點
infura_url = "https://mainnet.infura.io/v3/YOUR_INFURA_PROJECT_ID"
w3 = Web3(Web3.HTTPProvider(infura_url))# 檢查連接
print(f"是否已連接: {w3.isConnected()}")
print(f"最新區塊號: {w3.eth.block_number}")# 獲取賬戶余額
address = "0x742d35Cc6634C0532925a3b844Bc454e4438f44e"  # 示例地址
balance = w3.eth.get_balance(address)
print(f"余額: {w3.fromWei(balance, 'ether')} ETH")

智能合約交互

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# 合約ABI示例
contract_abi = '''
[{"inputs": [],"name": "get","outputs": [{"name": "","type": "uint256"}],"stateMutability": "view","type": "function"},{"inputs": [{"name": "x","type": "uint256"}],"name": "set","outputs": [],"stateMutability": "nonpayable","type": "function"}
]
'''# 合約地址
contract_address = "0x1234567890123456789012345678901234567890"# 創建合約實例
contract = w3.eth.contract(address=contract_address, abi=contract_abi)# 調用只讀函數
current_value = contract.functions.get().call()
print(f"當前值: {current_value}")# 發送交易(需要賬戶和私鑰)
'''
account = "0xYourAccountAddress"
private_key = "YourPrivateKey"
nonce = w3.eth.get_transaction_count(account)
tx = contract.functions.set(42).buildTransaction({'chainId': 1,'gas': 200000,'gasPrice': w3.toWei('50', 'gwei'),'nonce': nonce
})
signed_tx = w3.eth.account.sign_transaction(tx, private_key)
tx_hash = w3.eth.send_raw_transaction(signed_tx.rawTransaction)
print(f"交易哈希: {tx_hash.hex()}")
'''

智能合約開發

Solidity基礎合約

solidity

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// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;contract SimpleStorage {uint256 private value;event ValueChanged(uint256 newValue);function get() public view returns (uint256) {return value;}function set(uint256 newValue) public {value = newValue;emit ValueChanged(newValue);}
}

使用Brownie部署合約

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from brownie import accounts, SimpleStoragedef deploy_simple_storage():# 加載賬戶account = accounts[0]# 部署合約simple_storage = SimpleStorage.deploy({"from": account})# 初始值initial_value = simple_storage.get()print(f"初始值: {initial_value}")# 更新值transaction = simple_storage.set(42, {"from": account})transaction.wait(1)  # 等待1個區塊確認# 新值updated_value = simple_storage.get()print(f"更新后的值: {updated_value}")return simple_storagedef main():deploy_simple_storage()

https://ethereum.org/static/8ea7775026b7fac7b16188a50a60f70d/302a4/developers.png

NFT開發實戰

ERC721合約示例

solidity

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// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/utils/Counters.sol";contract MyNFT is ERC721 {using Counters for Counters.Counter;Counters.Counter private _tokenIds;constructor() ERC721("MyNFT", "MNFT") {}function mintNFT(address recipient, string memory tokenURI)publicreturns (uint256){_tokenIds.increment();uint256 newItemId = _tokenIds.current();_mint(recipient, newItemId);_setTokenURI(newItemId, tokenURI);return newItemId;}
}

使用Python鑄造NFT

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from brownie import accounts, network, config, MyNFT
from scripts.helpful_scripts import get_account
from pathlib import Path
import requests
import jsondef deploy_and_mint():account = get_account()my_nft = MyNFT.deploy({"from": account})# 上傳元數據到IPFStoken_uri = upload_to_ipfs("nft_metadata.json")# 鑄造NFTtx = my_nft.mintNFT(account, token_uri, {"from": account})tx.wait(1)print(f"NFT鑄造成功！查看地址: {my_nft.address}")def upload_to_ipfs(filepath):with Path(filepath).open("rb") as fp:file_binary = fp.read()ipfs_url = "http://127.0.0.1:5001"endpoint = "/api/v0/add"response = requests.post(ipfs_url + endpoint, files={"file": file_binary})ipfs_hash = response.json()["Hash"]return f"ipfs://{ipfs_hash}"def main():deploy_and_mint()

https://miro.medium.com/max/1400/1*8NgGYtqkYOwesVQdI3VQYw.png

DeFi應用開發

代幣合約(ERC20)

solidity

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// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;import "@openzeppelin/contracts/token/ERC20/ERC20.sol";contract MyToken is ERC20 {constructor(uint256 initialSupply) ERC20("MyToken", "MTK") {_mint(msg.sender, initialSupply);}
}

查詢代幣余額

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from web3 import Web3# 連接節點
w3 = Web3(Web3.HTTPProvider("https://mainnet.infura.io/v3/YOUR_PROJECT_ID"))# ERC20 ABI片段
erc20_abi = '''
[{"constant": true,"inputs": [{"name": "_owner", "type": "address"}],"name": "balanceOf","outputs": [{"name": "balance", "type": "uint256"}],"type": "function"}
]
'''# 代幣合約地址
token_address = "0x6B175474E89094C44Da98b954EedeAC495271d0F"  # DAI合約
user_address = "0xYourWalletAddress"# 創建合約實例
contract = w3.eth.contract(address=token_address, abi=erc20_abi)# 查詢余額
balance = contract.functions.balanceOf(user_address).call()
print(f"代幣余額: {balance / 10**18}")  # 假設代幣有18位小數

區塊鏈數據分析

分析交易數據

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import pandas as pd
from web3 import Web3w3 = Web3(Web3.HTTPProvider("https://mainnet.infura.io/v3/YOUR_PROJECT_ID"))def get_block_data(block_number):block = w3.eth.get_block(block_number, full_transactions=True)return {"block_number": block.number,"timestamp": block.timestamp,"miner": block.miner,"gas_used": block.gasUsed,"gas_limit": block.gasLimit,"transaction_count": len(block.transactions)}# 獲取最近10個區塊數據
blocks_data = [get_block_data(w3.eth.block_number - i) for i in range(10)]
df = pd.DataFrame(blocks_data)# 數據分析
print(df.describe())
print("\nGas使用率:")
df['gas_usage'] = df['gas_used'] / df['gas_limit']
print(df[['block_number', 'gas_usage']])

可視化交易趨勢

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import matplotlib.pyplot as plt# 準備數據
df['datetime'] = pd.to_datetime(df['timestamp'], unit='s')# 創建圖表
plt.figure(figsize=(12, 6))
plt.plot(df['datetime'], df['gas_usage'], marker='o')
plt.title('區塊Gas使用率趨勢')
plt.xlabel('時間')
plt.ylabel('Gas使用率')
plt.grid(True)
plt.savefig('gas_usage_trend.png')
plt.show()

https://www.researchgate.net/publication/338442131/figure/fig1/AS:842381179748352@1577724938245/Blockchain-data-analysis-process.png

安全最佳實踐

智能合約安全檢測

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from slither import Slither
from slither.detectors import all_detectorsdef analyze_contract(contract_path):# 加載合約slither = Slither(contract_path)# 運行所有檢測器detectors = [getattr(all_detectors, d) for d in all_detectors.__all__]print(f"分析合約: {contract_path}")print("=" * 50)for detector in detectors:detector = detector(slither)detector_results = detector.detect()if detector_results:print(f"\n{detector.ARGUMENT}:")for result in detector_results:print(f"- {result['description']}")print(f"  位置: {result['source_mapping']}")# 分析合約
analyze_contract("SimpleStorage.sol")

常見漏洞防護

重入攻擊防護:

solidity

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// 使用OpenZeppelin的ReentrancyGuard
import "@openzeppelin/contracts/security/ReentrancyGuard.sol";contract SecureContract is ReentrancyGuard {function safeWithdraw() public nonReentrant {// 提款邏輯}
}

整數溢出防護:

solidity

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// 使用SafeMath(0.8.0+版本已內置)
import "@openzeppelin/contracts/utils/math/SafeMath.sol";contract SafeMathExample {using SafeMath for uint256;function safeAdd(uint256 a, uint256 b) public pure returns (uint256) {return a.add(b);}
}

Web3開發工具鏈

工具名稱	用途	適用場景
Web3.py	以太坊交互庫	后端服務、腳本
Brownie	開發框架	合約測試、部署
Hardhat	開發環境	專業合約開發
Ganache	本地測試鏈	開發測試
Infura/Alchemy	節點服務	生產環境連接
OpenZeppelin	合約庫	安全合約開發
IPFS	去中心化存儲	NFT元數據存儲

去中心化應用(DApp)架構

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dapp_project/
├── client/              # 前端代碼
│   ├── public/          # 靜態文件
│   └── src/             # React/Vue代碼
├── contracts/           # 智能合約
│   ├── contracts/       # Solidity代碼
│   ├── tests/           # 合約測試
│   └── scripts/         # 部署腳本
├── backend/             # 后端服務(可選)
│   ├── api/             # API路由
│   └── services/        # 業務邏輯
└── docs/                # 項目文檔

前端集成示例

javascript

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import { ethers } from "ethers";
import ABI from "./contractABI.json";async function connectWallet() {if (window.ethereum) {try {// 請求賬戶訪問const accounts = await window.ethereum.request({ method: "eth_requestAccounts" });const provider = new ethers.providers.Web3Provider(window.ethereum);const signer = provider.getSigner();// 合約實例const contractAddress = "0x123...";const contract = new ethers.Contract(contractAddress, ABI, signer);// 調用合約const value = await contract.get();console.log("當前值:", value.toString());} catch (error) {console.error("用戶拒絕訪問:", error);}} else {alert("請安裝MetaMask!");}
}