Question

我想添加每个的库存值并打印出新的总数：

prices = {
    "banana" : 4,
    "apple"  : 2,
    "orange" : 1.5,
    "pear"   : 3,
}
stock = {
    "banana" : 6,
    "apple"  : 0,
    "orange" : 32,
    "pear"   : 15,
}



for key in prices:
    total = 0
    inventory = (prices[key] * stock[key])
    print key 
    print "inventory value: %s" % (inventory)
    total = total + inventory

print total

Answer 1

您的错误是您在每次迭代时重置total。

您可以通过使用理解来避免这些错误，这些理解可确保为这类问题提供适当的控制流程：

total = sum(p * stock.get(key,0) for key,p in prices.items())

它比经典循环快得多（并且迭代密钥和项目都可以保存对价格项目的访问权限）并作为最后一个奖励：tf项目没有库存，不会崩溃但会产生0

Answer 2

将total = 0移出循环

prices = {
    "banana" : 4,
    "apple"  : 2,
    "orange" : 1.5,
    "pear"   : 3,
}
stock = {
    "banana" : 6,
    "apple"  : 0,
    "orange" : 32,
    "pear"   : 15,
}


total = 0
for key in prices:
    inventory = (prices[key] * stock[key])
    print key 
    print "inventory value: %s" % (inventory)
    total = total + inventory

print total

Python：在for循环中添加结果

2 个答案: