Question

我有一个元组列表，我想遍历它并计算总成本。我想得到橙色的总成本加上香蕉的总成本。例如，5.26*8 + 2.00* 10找出总费用。

如何访问这些值？我尝试访问例如5.26 using b[1]*b[2]，但出现错误。

def totalcost(shoping):
    for a in shoping:
        for b in a:
        total1=b[1]*b[2]
        print(total1)

shoping=[("orange",5.26,8),("banana",2.00,10)]
totalcost(shoping)

Answer 1

一种方法是将每个元组解包为三个变量：

def get_total_cost(shopping):
    total_cost = 0
    for line_item in shopping:
        product, cost, quantity = line_item  # Unpack the tuple
        total_cost += quantity * cost
    return total_cost

shopping=[("orange", 5.26, 8), ("banana", 2.00, 10)]
print(get_total_cost(shopping))

一个人可以将解压缩与循环结合起来

def get_total_cost(shopping):
    total_cost = 0
    for product, cost, quantity in shopping:
        total_cost += quantity * cost
    return total_cost

可以将整个计算写为一个generator expression：

def get_total_cost(shopping):
    return sum(quantity * cost for product, cost, quantity in shopping)

为清楚起见，我给product起了一个名字。但是，在这样的代码中，习惯上用_代替未使用的变量：

def get_total_cost(shopping):
    return sum(quantity * cost for _, cost, quantity in shopping)

为完整起见，我将提到可以通过索引访问元组元素：

    return sum(line_item[1] * line_item[2] for line_item in shopping)

尽管在我看来，这比使用命名变量的可读性要差得多。

最后，如果您使用的是Python 3.7（or 3.6），则应考虑使用dataclasses。如果您使用的是Python的早期版本，则可以选择collections.namedtuple。

Answer 2

尝试以下代码段：

def totalcost(shoping):
    shoping = [list(i) for i in shoping ] 
    x = 0
    for i in shoping:
        x += i[1]*i[2]
    return x 
shoping=[("orange",5.26,8),("banana",2.00,10)]
print(totalcost(shoping))
#62.08

Answer 3

您在 a 中的 for 循环中有元组，以便可以从该元组中分割值。

def totalcost(shoping):
    for a in shoping:
        total1=a[1]*a[2]
        print(total1)

shoping=[("orange",5.26,8),("banana",2.00,10)]
totalcost(shoping)

遍历元组列表

3 个答案: