循环未运行并在第一次迭代中受到打击 - Python 背包问题（无错误）

Question

自己是 Python 的新手，并在已经运行的代码上尝试我的技能。 无法获得所需的输出作为输出列表，而只能获得第一个输入和详细信息。

功能代码块。 块 1

class Food(object):
    def __init__(self,n,v,w):
        self.name=n
        self.value=v
        self.calories=w
        
    def getValue(self):
        return self.value
    
    def getCost(self):
        return self.calories
    
    def density(self):
        return self.getValue()/self.getCost()
    
    def __str__(self):
        return self.name + ': <'+str(self.value) +','+str(self.calories)+'>'

块 2

def buildMenu(names,values,calories):
    menu=[]
    for i in range(len(values)):
        menu.append(Food(names[i],values[i],calories[i]))
        return menu

块 3

def greedy(items,maxCost,keyFunction):
    itemsCopy=sorted(items,key=keyFunction,reverse=True)
    result=[]
    totalValue,totalCost=0.0,0.0
    
    for i in range(len(itemsCopy)):
        if(totalCost+itemsCopy[i].getCost())<=maxCost:
            result.append(itemsCopy[i])
            totalCost+=itemsCopy[i].getCost()
            totalValue+=itemsCopy[i].getValue()
    return (result,totalValue)

块 4

def testGreedy(items,constraint,keyFunction):
    taken,val=greedy(items,constraint,keyFunction)
    print('Total value of items taken',val)
    for item in taken:
        print('  ',item)

第 5 块

def testGreedys(foods,maxUnits):
    print('Use greedy by value to allocate',maxUnits,'calories')
    testGreedy(foods,maxUnits,Food.getValue)
    print('\nUse greedy by cost to allocate',maxUnits,'calories')
    testGreedy(foods,maxUnits,lambda x:1/Food.getCost(x)) 
    print('\nUse greedy by density to allocate',maxUnits,'calories')
    testGreedy(foods,maxUnits,Food.density)

主要代码块和输入。

names=['wine','beer','pizza','burger','fries','cola','apple','donut','cake']
values=[89,90,95,100,90,79,50,10]
calories=[123,154,258,354,365,150,95,195]
foods=buildMenu(names,values,calories)
testGreedys(foods,750)

下面的当前输出仅采用第一个元素。实际上，它应该针对名称中的整个输入项列表运行。

Use greedy by value to allocate 750 calories
Total value of items taken 89.0
   wine: <89,123>

Use greedy by cost to allocate 750 calories
Total value of items taken 89.0
   wine: <89,123>

Use greedy by density to allocate 750 calories
Total value of items taken 89.0
   wine: <89,123>

请求您帮助调试并找出完整循环未按预期运行的原因。

Answer 1

当您构建菜单时，您对menu return处于循环中。 这会导致它只返回菜单中的一项，将其移回一个缩进。

def buildMenu(names,values,calories):
    menu=[]
    for i in range(len(values)):
        menu.append(Food(names[i],values[i],calories[i]))
    return menu

Total value of items taken 318.0
   apple: <50,95>
   wine: <89,123>
   cola: <79,150>
   beer: <90,154>
   donut: <10,195>