我正在用python做一个加油站项目，有一个错误

Question

print ("Welcome to the Gas Station!")
infiniteLoop = True
total = 0  
while True and infiniteLoop :
   
   print ("\n Gasoline \n Market \n Restaurant \nTotal \n quit to exit")
   select = input("Select One:")
   
   if select == "Gasoline":
       select1 = input("92 - 1 manat \n95 - 1.40 manat \n Diesel - 0.90 cents \n Premium - 2 manat \nWhat Gasoline Do You Want:")
       l = int(input("type liter:"))
       if select1 == "92":
           a = l * 1
           total = total + a
           print(a, "Manat")
           print("Gasoline Injected.")
       elif select1 == "95":
            b = l * 1.40
            total+= b   # update total amount
            b = print(b, "Manat")
            print("Gasoline Injected.")

       elif select1 == "Diesel": # Diesel needs to be String "Diesel"
            c = l * 1.90 
            total = total + c  # update total
            print(c, "Manat")
            print("Gasoline Injected.")
       elif select1 == "Premium": # Premium needs to be sting, in your code has no quote
            d = l * 2.0
            total = total + d
            print(d, "Manat")
            print("Gasoline Injected.")
            
   elif select == "Total":
        print("Total Amount:", total)
    # terminate infinite loop 
   elif select == 'quit':
       infiniteLoop = False

我是Python新手，我正在做一个加油站项目，我还没有完成它，当我在代码中选择一个总数时，它说没有“a”元素，有人能帮忙吗

Answer 1

我认为问题在于，在if/elif语句中声明了变量a、b、c和d。这意味着它们的范围在这些语句中

什么是示波器？这是代码的“区域”，您的变量将被识别为“存在”

例如：

def foo(a) :
    if a is true :
        b = "bar"
    print(b)

在这种情况下，b的作用域在if语句中，if中此赋值之后的所有内容都将访问它。因此，在print(b)调用的时刻，b是未知的，因为我们在范围之外

因此，为了解决问题，您应该在ifs之外定义变量。像这样：

a = 0
b = 0
c = 0
d = 0
if(#####)
    if select1 == 92:
        a = print(l * 1, "Manat")
        print("Gasoline Injected.")
    elif select1 == 95:
        b = print(l * 1.40, "Manat")
        print("Gasoline Injected.")
    elif select1 == Diesel:
        c = print(l * 0.90, "Manat")
        print("Gasoline Injected.")
    elif select1 == Premium:
        d = print(l * 2.0, "Manat")
        print("Gasoline Injected.")
if select == "Total":
    print("Total Amount:", a + b + c + d)

第二点，python中的print函数的返回值是None，这意味着您将None赋值给变量a、b、c、d

因此，要纠正你的a、b、c、d，你应该：

a = l * 1
b = l * 1.40
c = l * 0.90
d = l * 2

Answer 2

两个问题

• 并非所有的if-elif分支都保证发生在“total”之前，因此，当您尝试打印a+b+c+d时，某些变量可能不存在
• 您将调用print(...)的结果分配给a, b, c, d，即None

Answer 3

代码中的小问题

---

a。字符串“Diesel”不等于Diesel

b。压痕

c。可变范围等

不管怎样，这里有一个工作代码，运行它并检查你的代码有什么问题

print ("Welcome to the Gas Station!")
infiniteLoop = True
total = 0  
while True and infiniteLoop :
   
   print ("\n Gasoline \n Market \n Restaurant \nTotal \n quit to exit")
   select = input("Select One:")
   
   if select == "Gasoline":
       select1 = input("92 - 1 manat \n95 - 1.40 manat \n Diesel - 0.90 cents \n Premium - 2 manat \nWhat Gasoline Do You Want:")
       l = int(input("type liter:"))
       if select1 == "92":
           a = l * 1
           total = total + a
           print(a, "Manat")
           print("Gasoline Injected.")
       elif select1 == "95":
            b = l * 1.40
            total+= b   # update total amount
            b = print(b, "Manat")
            print("Gasoline Injected.")

       elif select1 == "Diesel": # Diesel needs to be String "Diesel"
            c = l * 1.90 
            total = total + c  # update total
            print(c, "Manat")
            print("Gasoline Injected.")
       elif select1 == "Premium": # Premium needs to be sting, in your code has no quote
            d = l * 2.0
            total = total + d
            print(d, "Manat")
            print("Gasoline Injected.")
            
   elif select == "Total":
        print("Total Amount:", total)
    # terminate infinite loop 
   elif select == 'quit':
       infiniteLoop = False