Question

我有以下代码，如果发生某种可能性，我希望它跳回到一行：

number_of_10ct = int(input("How many 10 Cent coins would you like to insert? "))
while number_of_10ct < 0:
    number_of_10ct = int(input("Please enter a positive number."))
number_of_20ct = int(input("How many 20 Cent coins would you like to insert? "))
while number_of_20ct < 0:
    number_of_20ct = int(input("Please enter a positive number."))
number_of_50ct = int(input("How many 50 Cent coins would you like to insert? "))
while number_of_50ct < 0:
    number_of_50ct = int(input("Please enter a positive number."))
number_of_100ct = int(input("How many 1 Rand coins would you like to insert? "))
while number_of_100ct < 0:
    number_of_100ct = int(input("Please enter a positive number."))
number_of_200ct = int(input("How many 2 Rand coins would you like to insert? "))
while number_of_200ct < 0:
    number_of_200ct = int(input("Please enter a positive number."))

number_of_500ct = int(input("How many 5 Rand coins would you like to insert? "))
while number_of_500ct < 0:
    number_of_500ct = int(input("Please enter a positive number."))

# Creating a variable to store the total amount of
# money inserted into the vending machine.
change = round(((number_of_10ct * 0.10) +
                (number_of_20ct * 0.20) + 
                (number_of_50ct * 0.50) + 
                (number_of_100ct * 1.00) +
                (number_of_200ct * 2.00) +
                (number_of_500ct * 5.00)),
               2)
# Informing the user how much they have entered in total.
print("\n")
print ('You have a credit of' ,change, 'ZAR')

while change > 0:
    customer_choice = input(("What would you like to buy?"
                             "Type N when you are finished \n"))
    if (customer_choice == "Kleiner Brauner" or
        customer_choice == "kleiner brauner" and
        change >= product_1_price):
        print ("You have chosen a", product_1,
               "these cost", product_1_price, "each,")
        change = round((change - product_1_price),2)
        print ("You have this much money remaining: R", change)
    elif (customer_choice == "Kakao" or
          customer_choice == "kakao" and
          change >= product_2_price):
        print ("You have chosen a", product_2,
               "these cost", product_2_price, "each,")
        change = round((change - product_2_price),2)
        print ("You have this much money remaining: R", change)
    elif customer_choice == "N" or customer_choice == "n":
        break
    elif change <= 0:
        print ("You have run out of money.")
        break
    else:
        print ("There has been an error or you may not have enough credit.")

我希望发生的事情是：如果change = round((change - product_1_price),2)最终会被否定，那么我希望程序返回到顶部（number_of_10ct = int(input("How many 10 Cent coins would you like to insert? "))）并允许用户输入更多“钱”

我该怎么做？

Answer 1

您可以做的是将所有代码放在一个额外的while循环中，该循环将继续运行，直到change变为正数（因此您需要先将change初始化为负值循环）。

change = -1

while change < 0:
    # All the rest of your code (re-indented to be under this while loop)

这样，您将在更改设置为正常值后输入while change > 0循环。一旦change变为负数，那么您就会离开此循环并返回顶部，用户可以在其中添加硬币。

然后，如果客户在使用所有更改之前决定不购买任何内容，那么change仍然是正面的，您将退出主while change < 0循环。

Answer 2

使用while循环和continue语句：

while True:
  dostuff()
  if goback():
    continue  # back to start of loop
  else:
    break     # code after the loop

如何让python程序循环回到某一行

2 个答案: