如何使 arguments 在 python 中不特定？

Question

我在 python 中有一個披薩店成本計算器的代碼，它計算下訂單后的成本，其中可以包括披薩、飲料、雞翅和優惠券。 不一定要有所有這些 arguments，它會有各種各樣的。 這就是我卡住的地方。 我有代碼，但我需要使用默認值 Arguments 來制作它，以便插入任何數量的 arguments 都會產生有效的 output。 （關於位置參數的東西）

這是代碼：

def pizza_cost(pizorders):
    total = 0
    for order in pizorders:
        total += 13
        if "pepperoni" in order:
            total = total + (x.count("pepperoni") * 1)
        if "mushroom" in order:
            total = total + (x.count("mushroom") * 0.5)
        if "olive" in order:
            total = total + (x.count("olive") * 0.5)
        if "anchovy" in order:
            total = total + (x.count("anchovy") * 2)
        if "ham" in order:
            total = total + (x.count("ham") * 1.5)
    return total

def drink_cost(driorders):
    total = 0
    for order in driorders:
        if order == "small":
            total = total + (x.count("small") * 2)
        if order == "medium":
            total = total + (x.count("medium") * 3)
        if order == "large":
            total = total + (x.count("large") * 3.5)
        if order == "tub":
            total = total + (x.count("tub") * 3.75)
    return total

def wing_cost(wingorders):
    total = 0
    for order in wingorders:
        if order == 10:
            total += 5
        if order == 20:
            total += 9
        if order == 40:
            total += 17.5
        if order == 100:
            total += 48
    return total


def cost_calculator(*pizzas, *drinks, *wings, *coupon):
    total = 0
    total += pizza_cost(pizzas)
    total += drink_cost(drinks)
    total += wing_cost(wings)
    tax = total * 0.0625
    discount = total * coupon
    total += tax
    total -= discount
    return total

這是錯誤：

   TypeError                                 Traceback (most recent call last)
~/opt/anaconda3/lib/python3.7/site-packages/bwsi_grader/__init__.py in compare_functions(student, soln, fn_args, fn_kwargs, function_name, comparison_function)
    110     try:
--> 111         student_out = student(*fn_args, **fn_kwargs)
    112     except Exception as e:

TypeError: cost_calculator() missing 3 required positional arguments: 'drinks', 'wings', and 'coupon'

During handling of the above exception, another exception occurred:

StudentError                              Traceback (most recent call last)
<ipython-input-13-322b790cbb8b> in <module>
      1 # Execute this cell to grade your work
      2 from bwsi_grader.python.pizza_shop import grader
----> 3 grader(cost_calculator)

~/opt/anaconda3/lib/python3.7/site-packages/bwsi_grader/python/pizza_shop.py in grader(student_func)
    191     for pizzas, items in zip(std_pizzas, std_orders):
    192         compare_functions(student=student_func, soln=soln,
--> 193                           fn_args=tuple(pizzas), fn_kwargs=items)
    194 
    195     for i in range(1000):

~/opt/anaconda3/lib/python3.7/site-packages/bwsi_grader/__init__.py in compare_functions(student, soln, fn_args, fn_kwargs, function_name, comparison_function)
    111         student_out = student(*fn_args, **fn_kwargs)
    112     except Exception as e:
--> 113         raise StudentError(f"\nCalling \n\t{pad_indent(sig, ln=4)}\nproduces the following error:"
    114                            f"\n\t{type(e).__name__}:{e}"
    115                            f"\nPlease run your function, as displayed above, in your Jupyter "

StudentError: 
Calling 
    student_function([])
produces the following error:
    TypeError:cost_calculator() missing 3 required positional arguments: 'drinks', 'wings', and 'coupon'
Please run your function, as displayed above, in your Jupyter notebook to get a detailed stacktrace of the error, and debug your function.

Answer 1

當您聲明一個不使用默認 arguments 的 function 時，Python 希望您必須為每個參數輸入一個輸入。 默認參數將允許您不為參數添加任何內容。

def cost_calculator(pizza=[], drinks=[], wings=[], coupon=0.0):

     ''' your code here '''

非默認 arguments 被稱為位置 arguments 因為它們總是必須輸入並且必須以正確的順序輸入。

對於默認 arguments，您應該確保在進行 function 調用時輸入參數的名稱：

cost_calculator(drinks=['small', 'small', 'large'], coupon=0.2)

我認為這應該在分級代碼中起作用。 他們正在使用一種稱為字典解包的方法，該方法允許您將所有默認參數作為字典 object 提交，按慣例稱為kwargs ：