Python错误，分配前可能会引用局部变量，if条件之外的变量

Question

我是python编程实践的新手，做了我的第一个基本程序

我必须访问并打印if函数中的局部变量，并且如果我尝试访问它，它表明可能引用了局部变量

这是完整的代码

def main():
print("Please place your order by filling the options")

name = input("What is your name ")
while not name.isalpha():
    print("invalid name")

age = input("What is your age ")
if not age.isdigit():
    print("Please type in correct form")
    if age >= "50":
    print("you are not allowed!")
    sys.exit()

item_1 = "burger"
item_2 = "pizza"
print("what would you like to order?")

print(item_1 + "\n" + item_2)
order = input()

item_1_large = "large burger"
item_1_small = "small burger"

item_2_large = "large pizza"
item_2_small = "small pizza"

if order == item_1:
    print("What would you like to choose?")
    print(item_1_large + "\n" + item_1_small)
    selection_of_category = input()
elif order == item_2:
    print("What would you like to choose?")
    print(item_2_large + "\n" + item_2_small)
    selection_of_category = input()

print("How many ")
number_of_order = input()

burger_price_large = int(10)
burger_price_small = int(5)
pizza_price_large = int(15)
pizza_price_small = int(8)




if order == item_1_large:
    result = burger_price_large * int(number_of_order)
elif order == item_1_small:
    result = burger_price_small * int(number_of_order)
elif order == item_2_large:
    result = pizza_price_large * int(number_of_order)
elif order == item_2_small:
    result = pizza_price_small * int(number_of_order)



if order == item_1:
    print("Your Burger Order Has Been Placed")
elif order == item_2:
    print("Your Pizza Order Has Been Placed")
else:
    print("You have made wrong choice")

print("Dear Mr. " + name, "Your Total Bill is $" + str (result))
while True:
main()
if input("Would you like to order something? (Y/N)").strip().upper() != 'Y':
    today = date.today()
    print("Thank you for your order")
    print(today)
    break

而且我有以下错误打印（“亲爱的先生” +名称，“您的总帐单为$” + str（结果））UnboundLocalError：赋值之前引用了局部变量'result'

Answer 1

您的问题是仅在if和else-if语句下定义结果。 这意味着，如果if或else-if语句中的每个条件都失败，则不会定义结果，但是您将尝试使用其值。

您有两种解决此问题的方法：

1. 使最后一个elif成为全包，并为所有可能的阶值取一个值
2. 如果所有if＆elif条件均失败，则在最后一个elif之后使用另一个else将结果定义为类似“ N / A”的内容。