Replace Temp with Query

暫時變數很方便：能存程式碼所生值，讓其被引用；名稱也能解釋其意義，防止重複程式碼出現。
如果能改成函式會更好：函式減少引入一個參數，邏輯與原始函式間也設下明確邊界，並避免此計算邏輯在類似函式中重複出現。

此做法最能有效處理類別，因為成員都位於共用環境。
但它僅適合處理「被計算一次，之後皆為讀取」的暫時變數，不適合處理快照（snapshot）變數。

# Before
original_price = 200
discount_rate = 0.15
discount_amount = original_price * discount_rate
discounted_price = original_price - discount_amount
print(f"Discounted price: {discounted_price}")

# After
class PriceCalculator:
    def __init__(self, original_price, discount_rate):
        self.original_price = original_price
        self.discount_rate = discount_rate

    def discount_amount(self):
        return self.original_price * self.discount_rate

    def discounted_price(self):
        return self.original_price - self.discount_amount()

calculator = PriceCalculator(200, 0.15)
print(f"Discounted price: {calculator.discounted_price()}")