初学者 Python：AttributeError：'list' 对象没有属性
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/29335423/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Beginner Python: AttributeError: 'list' object has no attribute
提问by Charles Watson
The error says:
错误说：
AttributeError: 'list' object has no attribute 'cost'
I am trying to get a simple profit calculation to work using the following class to handle a dictionary of bicycles:
我正在尝试使用以下类来进行简单的利润计算来处理自行车字典：
class Bike(object):
def __init__(self, name, weight, cost):
self.name = name
self.weight = weight
self.cost = cost
bikes = {
# Bike designed for children"
"Trike": ["Trike", 20, 100],
# Bike designed for everyone"
"Kruzer": ["Kruzer", 50, 165]
}
When I try to calculate profit with my for statement, I get the attribute error.
当我尝试使用 for 语句计算利润时，出现属性错误。
# Markup of 20% on all sales
margin = .2
# Revenue minus cost after sale
for bike in bikes.values():
profit = bike.cost * margin
First, I don't know why it is referring to a list, and everything seems to be defined, no?
首先，我不知道为什么它指的是一个列表，而且一切似乎都已定义，不是吗？
采纳答案by jedwards
Consider:
考虑：
class Bike(object):
def __init__(self, name, weight, cost):
self.name = name
self.weight = weight
self.cost = cost
bikes = {
# Bike designed for children"
"Trike": Bike("Trike", 20, 100), # <--
# Bike designed for everyone"
"Kruzer": Bike("Kruzer", 50, 165), # <--
}
# Markup of 20% on all sales
margin = .2
# Revenue minus cost after sale
for bike in bikes.values():
profit = bike.cost * margin
print(profit)
Output:
输出：
33.0 20.0
The difference is that in your bikesdictionary, you're initializing the values as lists [...]. Instead, it looks like the rest of your code wants Bikeinstances. So create Bikeinstances: Bike(...).
不同之处在于，在您的bikes字典中，您将值初始化为列表[...]。相反，看起来您的其余代码需要Bike实例。所以创建Bike实例：Bike(...).
As for your error
至于你的错误
AttributeError: 'list' object has no attribute 'cost'
this will occur when you try to call .coston a listobject. Pretty straightforward, but we can figure out what happened by looking at where you call .cost-- in this line:
这样当您尝试调用将出现.cost一个上list对象。非常简单，但我们可以通过查看您调用的位置来弄清楚发生了什么.cost- 在这一行中：
profit = bike.cost * margin
This indicates that at least one bike(that is, a member of bikes.values()is a list). If you look at where you defined bikesyou can see that the values were, in fact, lists. So this error makes sense.
这表明至少有一个bike（即，一个成员bikes.values()是一个列表）。如果您查看定义的位置，bikes您会发现这些值实际上是列表。所以这个错误是有道理的。
But since your classhas a cost attribute, it looked like you were trying to use Bikeinstances as values, so I made that little change:
但是因为你的类有一个 cost 属性，看起来你试图使用Bike实例作为值，所以我做了一点改变：
[...] -> Bike(...)
and you're all set.
你已经准备好了。
回答by Jake Kreider
You need to pass the values of the dict into the Bikeconstructor before using like that. Or, see the namedtuple-- seems more in line with what you're trying to do.
Bike在使用之前，您需要将 dict 的值传递给构造函数。或者，查看namedtuple-- 似乎更符合您要执行的操作。
回答by Ygedey
They are lists because you type them as lists in the dictionary:
它们是列表，因为您在字典中将它们作为列表键入：
bikes = {
# Bike designed for children"
"Trike": ["Trike", 20, 100],
# Bike designed for everyone"
"Kruzer": ["Kruzer", 50, 165]
}
You should use the bike-class instead:
您应该改用自行车类：
bikes = {
# Bike designed for children"
"Trike": Bike("Trike", 20, 100),
# Bike designed for everyone"
"Kruzer": Bike("Kruzer", 50, 165)
}
This will allow you to get the cost of the bikes with bike.cost as you were trying to.
这将使您能够像您尝试使用的那样通过 bibk.cost 获得自行车的成本。
for bike in bikes.values():
profit = bike.cost * margin
print(bike.name + " : " + str(profit))
This will now print:
现在将打印：
Kruzer : 33.0
Trike : 20.0
