錯誤的循環和返回變量

Question

我的代碼如下檢查輸入（數量）是一個數字。如果第一次是數字，它會返回數字。但是，如果您要輸入一個字母，然後當函數循環輸入一個數字時，將返回「0」而不是您輸入的數字。

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 

我正在循環功能嗎？

Answer 1

你的功能實際上是不正確的，你正在使用while循環連同recursion function，在這種情況下這是不必要的。雖然，您可以嘗試以下代碼，該代碼根據您的功能稍微修改，但只使用while循環。

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 

---

儘管實際上你可以在一個更簡單的方式做到了這一點，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，嘗試以下操作：

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() 

請注意如果你想要VA當你輸入一個數字時，最終返回，你需要在else中使用return quantityFunction()。否則最終不會返回任何內容。這也解釋了你爲什麼在你第一次輸入號碼時輸入號碼的問題，但不能在之後輸入號碼。