错误的循环和返回变量

Question

我的代码如下检查输入（数量）是一个数字。如果第一次是数字，它会返回数字。但是，如果您要输入一个字母，然后当函数循环输入一个数字时，将返回“0”而不是您输入的数字。

def quantityFunction(): 
    valid = False 
    while True: 
      quantity = input("Please enter the amount of this item you would like to purchase: ") 
      for i in quantity: 
       try: 
        int(i) 
        return int(quantity) 
       except ValueError: 
        print("We didn't recognise that number. Please try again.") 
        quantityFunction() 
        return False 

我正在循环功能吗？

Answer 1

你的功能实际上是不正确的，你正在使用while循环连同recursion function，在这种情况下这是不必要的。虽然，您可以尝试以下代码，该代码根据您的功能稍微修改，但只使用while循环。

def quantityFunction(): 
    valid = False 
    while not valid: 
     quantity = input("Please enter the amount of this item you would like to purchase: ") 
     for i in quantity: 
      try: 
       int(i) 
       return int(quantity) 
      except ValueError: 
       print("We didn't recognise that number. Please try again.") 
       valid = False 
       break 

---

尽管实际上你可以在一个更简单的方式做到了这一点，如果你想使用while loop：

def quantityFunction(): 
    while True: 
     quantity = input("Please enter the amount of this item you would like to purchase: ") 
     if quantity.isdigit(): 
      return int(quantity) 
     else: 
      print("We didn't recognise that number. Please try again.") 

如果你真的想用recursive function，尝试以下操作：

def quantityFunction1(): 
    quantity = input("Please enter the amount of this item you would like to purchase: ") 
    if quantity.isdigit(): 
     return int(quantity) 
    else: 
     print("We didn't recognise that number. Please try again.") 
     return quantityFunction() 

请注意如果你想要VA当你输入一个数字时，最终返回，你需要在else中使用return quantityFunction()。否则最终不会返回任何内容。这也解释了你为什么在你第一次输入号码时输入号码的问题，但不能在之后输入号码。