Python的排序錯誤

Question

當我嘗試在Python排序我的名單，我得到以下錯誤：

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 

下面是我使用的代碼。我想知道如何對包含列表的列表進行排序。還想知道爲什麼我的數據將被打印兩次，以及如何更好地格式化打印輸出以便它對應於正確的列。 （沒有導入下載）

任何幫助將不勝感激。

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) 

我已經加了我所有的代碼如下：

# 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) 

目前打印這樣的：

名稱計量價格單價

looooool 1.0 10.0 10.0
looooool 1.0 10.0 10.0
哈哈1.0 1.0 1.0
過程完成退出代碼0

Answer 1

您的代碼似乎預計products列表中的每個列表都有4個元素（名稱，測量，價格和單價），但實際上您的數據只有兩個元素每個列表（用於芯片和飲料）。

然後當您嘗試對包含長度爲2的列表的products進行排序時，可以訪問lambda函數中的第4個值。這會觸發錯誤：只有兩個值，而不是4.

看起來您已將您想要結束的數據轉換爲products。相反的：

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

做：

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

或者更簡潔：

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