5 分钟搞定防御性编程：打造稳健的软件

import loggingimport threadingimport timefrom typing import Union
# 日志设置logging.basicConfig(level=logging.INFO, format="%(asctime)s - %(levelname)s - %(message)s")
class BankAccount:    """ A secure bank account implementing defensive programming practices"""        def __init__(self, account_number: str, initial_balance: Union[int, float] = 0):        assert isinstance(account_number, str), "Account number must be a string"        assert isinstance(initial_balance, (int, float)) and initial_balance >= 0, "Initial balance must be a positive number"                self.account_number = account_number        self.balance = initial_balance        self.lock = threading.Lock()  # Prevents race conditions in multithreading        logging.info(f"Account {self.account_number} created with balance ${self.balance}")
    def validate_amount(self, amount: Union[int, float]):        """ Validates deposit/withdrawal amounts"""        if not isinstance(amount, (int, float)) or amount <= 0:            raise ValueError("Amount must be a positive number")        def deposit(self, amount: Union[int, float]):        """ Securely deposits money into the account"""        self.validate_amount(amount)        with self.lock:            # 更新余额的原子操作            self.balance += amount            logging.info(f"Deposited ${amount} into account {self.account_number}. New balance: ${self.balance}")
    def withdraw(self, amount: Union[int, float]):        """ Withdraws money securely, ensuring no overdraft"""        self.validate_amount(amount)        with self.lock:            if amount > self.balance:                raise ValueError("Insufficient funds")            # 更新余额的原子操作            self.balance -= amount            logging.info(f"Withdrew ${amount} from account {self.account_number}. New balance: ${self.balance}")
    def get_balance(self) -> float:        """ Retrieves the current balance safely"""        with self.lock:            return self.balance
# **依赖 & 资源管理**def process_transactions(account: BankAccount):    """ Simulates multiple transactions with concurrency management"""    threads = []    for _ in range(3):        t1 = threading.Thread(target=account.deposit, args=(100,))        t2 = threading.Thread(target=account.withdraw, args=(50,))        threads.extend([t1, t2])
    for t in threads:        t.start()    for t in threads:        t.join()
# **错误处理 & 安全**def safe_transaction(account: BankAccount, transaction_type: str, amount: float):    """ Handles transactions with exception handling"""    try:        if transaction_type == "deposit":            account.deposit(amount)        elif transaction_type == "withdraw":            account.withdraw(amount)        else:            raise ValueError("Invalid transaction type")    except ValueError as e:        logging.error(f"Transaction error: {e}")
#**执行防御性编程**if __name__ == "__main__":    acc = BankAccount("1234567890", 500)        # 执行安全事务    safe_transaction(acc, "deposit", 200)    safe_transaction(acc, "withdraw", 800)  # Should fail (handled gracefully)        # 多线程并发    process_transactions(acc)        # 最终余额检查    logging.info(f"Final balance for account {acc.account_number}: ${acc.get_balance()}")