将变量从子例程全球化到另一个子例程

debugcn 发表于 Dev

匿名的

将变量从一个子例程传递到另一个子例程时遇到麻烦。

这是代码：

def loop1():
    try:
        age=int(input("How old are you? "))
    except ValueError:
        print ("Please enter a numerical integer of your age. For example: 19 ")
        print("")
        loop1()
    if age>0:
        program()

def program():
    print("")
    print("[1] - Knife / Spray Paint / Lottery Ticket ")
    print("[2] - Alcohol / Tobacco ")
    print("[3] - Anything else ")
    print("")
    loop2()

def loop2():
    try:
        item=int(input("What would you like to buy from the options above? "))
        print("")
    except ValueError:
        print ("Please enter a numerical integer of your item. For example (if you wanted to buy alcohol): 2 ")
        print("")
        loop2()
    if item>0:
        validation()

def validation(): 
    if item == 1 and 16>age :
        print("Sale Denied - Item cannot be sold to Under 16s. ")
    elif item == 1 and 16<age:
        print("Sale Accepted. ")

    elif item == 2 and 18>age:
        print("Sale Denied - Item cannot be sold to Under 18s. ")
    elif item == 2 and 25>age>18:
        print("Check ID before selling alcohol - Challenge 25. ")
    elif item == 2 and 18<age:
        print("Sale Accepted. ")

    elif item == 3:
        print("Sale Accepted. ")

loop1()

结果如下：

How old are you? 21

[1] - Knife / Spray Paint / Lottery Ticket 
[2] - Alcohol / Tobacco 
[3] - Anything else 

What would you like to buy from the options above? 2

Traceback (most recent call last):
  File "D:/Shop Program.py", line 48, in <module>
    loop1()
  File "D:/Test.py", line 9, in loop1
    program()
  File "D:/Shop Program.py", line 17, in program
    loop2()
  File "D:/Shop Program.py", line 28, in loop2
    validation()
  File "D:/Shop Program.py", line 33, in validation
    if item == 1 and 16>age :
NameError: global name 'item' is not defined

如您从上面的错误消息中看到的那样global name 'item' is not defined。我尝试将放置global item在上方def vaildation():，但仍然遇到相同的错误。

琼斯·哈珀

而不是使用global，这是一种不好的做法（在Python和其他地方），明确地传递item从loop2到validation：

def loop2(age):
    ...
    if item > 0:
        validation(item, age)
                 # ^ pass it here

def validation(item, age): 
             # ^ receive it here
    if item == 1 and 16 > age:
        ...

请注意，我对做了类似的事情age，应该在loop2调用时传递。使用递归进行输入验证不是理想的方法。请参阅要求用户提供输入信息，直到他们给出有效的替代方法答复为止。