Python排序

Question

当我尝试用python对列表排序时，出现以下错误：

Traceback (most recent call last):
  File "C:/Users/natep/OneDrive/Documents/I.T/Level 2/programing/Shop_list.py", line 81, in <module>
    products.sort(key = lambda  x:x[3], reverse=True)
Name        Measurement     Price       Unit Price
  File "C:/Users/natep/OneDrive/Documents/I.T/Level 2/programing/Shop_list.py", line 81, in <lambda>

products.sort(key = lambda  x:x[3], reverse=True)
Chips   Drink   
IndexError: list index out of range
50  2.0     
5.0     3.0     
2.5     1.0     
Chips   Drink   
50  2.0     
5.0     3.0     
2.5     1.0     
Process finished with exit code 1

下面是我正在使用的代码。我想知道如何对包含列表的列表进行排序。我还想知道为什么我的数据要打印两次，以及如何更好地格式化打印输出，使其与正确的列相对应。（不导入下载）

任何帮助都将不胜感激。你知道吗

unit_price = price / measurement
unit.append(unit_price)

products.append(name_sum)
products.append(mes_sum)
products.append(money_sum)
products.append(unit)
row_entry.append(products)

average = "The average product price is ${}".format(mean(money_sum))
highest = "The most expensive item is ${}".format(max(money_sum))
low = "The cheapest item is ${}".format(min(money_sum))

print()
print("Name\t\tMeasurement\t\tPrice\t\tUnit Price" )
for item in products:
  print("")
  for data in item:
    print(data, "\t", end='')

products.sort(key = lambda  x:x[3], reverse=True)

我在下面添加了所有代码：

# Shopping list
from statistics import mean
from operator import itemgetter

def limit_check(type, question, low, high):

    valid = False
    error = "please enter values between {} and or equal to {}".format(low, 
high)
    while not valid:
        try:
            response = type(input(question))
            if low < response <= high:
                valid = True
                return response
            else:
                print(error)
        except ValueError:
            print(error)

products = []
mes_sum = []
money_sum = []
name_sum = []
unit = []
row_entry = []

money = float(input("please enter your budget: $"))

get_data = True
while get_data == True:

name = input("please enter product name: ")
if name.lower() == "xxx":
    break
else:
    name_sum.append(name)
    price = limit_check(float,"How much does the item cost", 0, money)
    money_sum.append(price)
    measurement = limit_check(int,"Please enter unit of measurement Push 1 
for kg, push 2 for g, push 3 for L, push 4 for mL",0,4)


    if measurement == int("1"):
        kg = limit_check(float, "Enter Kg: ", 0, 10)
        mes_sum.append(kg)

    elif measurement == int("2"):
        grams = limit_check(int, "Enter Grams: ", 0, 999)
        mes_sum.append(grams)

    elif measurement == int("3"):
        litres = limit_check(float, "Enter Litres: ", 0, 30)
        mes_sum.append(litres)

    elif measurement == int("4"):
        mL = limit_check(int, "Enter mL: ", 0, 999)
        mes_sum.append(mL)

    unit_price = price / measurement
    unit.append(unit_price)


    for i in range(len(name_sum)):
        products.append([name_sum[i], mes_sum[i], money_sum[i], unit[i]])

average = "The average product price is ${}".format(mean(money_sum))
highest = "The most expensive item is ${}".format(max(money_sum))
low = "The cheapest item is ${}".format(min(money_sum))



print()
print("Name\t\tMeasurement\t\tPrice\t\tUnit Price" )
for item in products:
  print("")
  for data in item:
      print(data, "\t", end='')

products.sort(key = lambda  x:x[1], reverse=True)

当前打印如下：

名称计量价格单价

Loooool 1.0 10.0 10.0
Loooool 1.0 10.0 10.0
lol 1.0 1.0 1.0
进程已完成，退出代码为0

Answer 1

您的代码似乎期望products列表中的每个列表都有4个元素（用于名称、度量、价格和单价），但实际上您的数据在每个列表中只有两个元素（用于薯片和饮料）。你知道吗

然后，当您尝试对包含长度为2的列表的products排序时，您将访问lambda函数中的第4个值。这会触发错误：只有两个值，而不是4。你知道吗

看起来您已经转置了想要在products中结束的数据。而不是：

products.append(name_sum)
products.append(mes_sum)
products.append(money_sum)
products.append(unit)

执行：

for i in range(len(name_sum)):
    products.append([name_sum[i], mes_sum[i], money_sum[i], unit[i]]) 

或者更紧凑地说：

products.extend(list(map(list, zip(*[name_sum, mes_sum, money_sum, unit]))))