我使用组合来显示背包中所有可能的项目子集，所以如果我有10个项目，具有不同的价值和重量它会显示项目的所有组合，总重量这是元组中的第二个位置（Id，Weight，Val）和总值，我的问题是我得到一个元组索引超出范围错误。
#Knapsack
from random import *
from itertools import *
#Creates List of Items, using N for Num of Items
#Weightmax for the max range of weights
#Valmax of max value range
#Each Item has a Id, Weight and Value.
#Represented as a tuple. [(Id,Weight,Value)]
def item_list(n,weightmax,valmax):
items = []
for i in range(1,n+1):
items.append((i,randrange(1,weightmax),randrange(1,valmax)))
return items
#----------------------------------------------------
#Is the Sack, Takes Items as a parameter, and Capacity
#Purpose is to find and print all possible combinations that
#Will fit in the sack,then print which subset has the best
#weight for value mix.
def knapsack(items,capacity):
sack = items
subs = []
print("------------------------------")
print("Subset,"," | ", "Total Weight", " | ", "Total Value")
for i in range(len(sack)+1):
print(i)
for j in combinations(items, i):
subs.append(j)
print(j," | ",j[i][1]," | ",j[i][2])
#------------------------------------
#Main, Asks for UserInput and allows you
#to re-enter mistypes.
def main():
choices = False
print("Welcome to the Knapsack Filler!")
print("Please Input the Following Parameters; ")
while choices is False:
knapcap = int(input("Enter Knapsack Max Capacity: "))
maxweight = int(input("Enter Max Range for Weights: "))
maxval = int(input("Enter Max Value Range for Weights: "))
numitems = int(input("Number of Items you wish to generate: "))
prompt= input("\n Y or N; Are you Sure about your Choices?: ")
if prompt.lower() =="yes" or "y":
choices = True
else:
pass
knapsack(item_list(numitems,maxweight,maxval),knapcap)
main()
错误：
Traceback (most recent call last):
File "C:\CS230\CS320_P2_Knapsack.py", line 54, in <module>
main()
File "C:\CS230\CS320_P2_Knapsack.py", line 53, in main
knapsack(item_list(numitems,maxweight,maxval),knapcap)
File "C:\CS230\CS320_P2_Knapsack.py", line 31, in knapsack
print(j," | ",j[i][1]," | ",j[i][2])
IndexError: tuple index out of range
示例输入：
Welcome to the Knapsack Filler!
Please Input the Following Parameters;
Enter Knapsack Max Capacity: **30**
Enter Max Range for Weights: **10**
Enter Max Value Range for Weights: **10**
Number of Items you wish to generate: **3**
Y or N; Are you Sure about your Choices?: Y
------------------------------
Subset, | Total Weight | Total Value
0
答案 0 :(得分：0)
这是一个难以回答的问题，因为您遇到的问题源于概念，但也存在代码中的架构难题。我已经用类似于我自己的方式重写了你的代码，希望看到“好的代码”可以帮助你弄清楚你可能出错的地方。
我所做的一些重大改变包括：
Item课程，使ID，重量和价值清晰易懂Sack类来抽象查找项目权重和值的子集的详细信息如果您还不知道如何使用课程，那么他们真的是很好的事情，如下面的代码所示。
<强>代码
#!/usr/bin/env python3
import random
import itertools
class Item:
def __init__(self, id, weight, value):
self.id = id
self.weight = weight
self.value = value
class Sack:
def __init__(self, items):
self.items = items
def weight(self):
return sum([x.weight for x in self.items])
def value(self):
return sum([x.value for x in self.items])
def ids(self):
return ', '.join([str(x.id) for x in self.items])
def __repr__(self): #What gets shown when you call the print function
return "{0:10} {1:10} {2}".format(self.weight(), self.value(), self.ids())
def powerset(iterable):
"""
powerset([1,2,3]) --> () (1,) (2,) (3,) (1,2) (1,3) (2,3) (1,2,3)
Source: https://docs.python.org/2/library/itertools.html
"""
s = list(iterable)
return itertools.chain.from_iterable(itertools.combinations(s, r) for r in range(len(s)+1))
def item_list(n,weightmax,valmax):
"""
Creates a list of randomly generated items
Arguments:
n Number of items to have in the sack
weightmax Weights are generated in the range [1,weightmax]
valuemax Values are generated in the range [1,valuemax]
Returns:
A list of [(Id,Weight,Value), (Id,Weight,Value), ...]
"""
items = []
for i in range(1,n+1):
items.append(Item(id=i, weight=random.randint(1,weightmax), value=random.randint(1,valmax)))
return items
def knapsack(items,capacity):
"""Find and print all the combinations of items that will fit into the sack.
Also print the most valuable combination.
Arguments:
items A list of items generated by item_list()
capacity The maximum weight the knapsack can hold
"""
print("------------------------------")
print("{0:>10} {1:>10} {2}".format("Weight","Value","Subset"))
subsets_that_fit = []
for sackitems in powerset(items):
sack = Sack(sackitems)
if sack.weight()>capacity:
continue
print(sack)
subsets_that_fit.append(sack)
best = max(subsets_that_fit, key=lambda x: x.value())
print("Best")
print(best)
def main():
choices = False
print("Welcome to the Knapsack Filler!")
print("Please Input the Following Parameters; ")
while choices is False:
knapcap = int(input("Enter Knapsack Max Capacity: "))
maxweight = int(input("Enter Max Range for Weights: "))
maxval = int(input("Enter Max Value Range for Weights: "))
numitems = int(input("Number of Items you wish to generate: "))
prompt = input("\n Y or N; Are you Sure about your Choices?: ")
if prompt.lower() =="yes" or "y":
choices = True
else:
pass
knapsack(item_list(numitems,maxweight,maxval),knapcap)
main()