Simple while loop in Python

Question

I am making a supermarket interface, and my program works fine if I run without going back. However, if userchoice = 2, I can't go back to userchoice = 1. I can only go to 2 or the options after it. I think there could be something wrong with my while loop.

apples = 0
mangoes = 0
print("Welcome to the CS110 Supermarket!")
print("1. Potatoes (0ドル.75 per potato")
print("2. Tomatoes (1ドル.25 per tomato")
print("3. Apples (0ドル.5 per apple")
print("4. Mangoes (1ドル.75 per mango")
print("5. Checkout")
user_choice = int(input())
total = total + potatoes*0.75 + tomatoes*1.25 + apples*0.5 + mangoes*1.75
while user_choice == 1:
 potatoes = int(input("How many potatoes?"))
 total = total + potatoes*0.75
 print("The total cost is $", total)
 print("Welcome to the CS110 Supermarket!")
 print("1. Potatoes (0ドル.75 per potato")
 print("2. Tomatoes (1ドル.25 per tomato")
 print("3. Apples (0ドル.5 per apple")
 print("4. Mangoes (1ドル.75 per mango")
 print("5. Checkout")
 user_choice = int(input())
while user_choice == 2:
 tomatoes = int(input("How many tomatoes?"))
 total = total + tomatoes*1.25
 print("The total cost is $", total)
 print("Welcome to the CS110 Supermarket!")
 print("1. Potatoes (0ドル.75 per potato")
 print("2. Tomatoes (1ドル.25 per tomato")
 print("3. Apples (0ドル.5 per apple")
 print("4. Mangoes (1ドル.75 per mango")
 print("5. Checkout")
 user_choice = int(input())
while user_choice == 3:
 apples=int(input("How many apples?"))
 total = total + apples*0.5
 print("The total cost is $", total)
 print("Welcome to the CS110 Supermarket!")
 print("1. Potatoes (0ドル.75 per potato")
 print("2. Tomatoes (1ドル.25 per tomato")
 print("3. Apples (0ドル.5 per apple")
 print("4. Mangoes (1ドル.75 per mango")
 print("5. Checkout")
 user_choice = int(input())
while user_choice == 4:
 mangoes = int(input("How many mangoes?"))
 total = total + mangoes*1.75
 print("The total cost is $",total)
 print("Welcome to the CS110 Supermarket!")
 print("1. Potatoes (0ドル.75 per potato")
 print("2. Tomatoes (1ドル.25 per tomato")
 print("3. Apples (0ドル.5 per apple")
 print("4. Mangoes (1ドル.75 per mango")
 print("5. Checkout")
 user_choice=int(input())
if user_choice == 5:
 print("The total cost is $",total)
 pay = float(input("Please enter an amount to pay for the fruits and vegetables: "))
 while pay < total:
 pay = float(input("Please enter an amount more than payment: "))
 change = pay - total
 print("Your change will be $", change)
 d5 = change // 5
 d1 = (change % 5) // 1
 quarter = ((change % 5) % 1) // 0.25
 dime = (((change % 5) % 1) % 0.25) // 0.1
 nickel = ((((change % 5) % 1) % 0.25) % 0.1) // 0.05
 penny = (((((change % 5) % 1) % 0.25) % 0.1) % 0.05) // 0.01
 print("Give the customer", d5, "5ドル note,", d1, "1ドル note,", quarter, "quarter,", dime, "dime,", nickel,"nickel,", penny, "penny.")

• Fred Larson: Try one while loop with an if for each of your options.

Answer 1

You're using more whiles than you need. rather than a while for each option, use only one loop, and several ifs for options:

while True:
 user_choice=int(input())
 if user_choice == 1:
 ...
 if user_choice == 2:
 ...
 ...
 if user_choice == 5:
 break # exit the loop with break

Answer 2

You could use an infinite loop while putting the user_input at the top of the loop. Then, you just have to use if conditions. You are currently using one loop per parameter. This is not going to work since you can't get out that loop to process an other choice.

while True:
 print("Welcome to the CS110 Supermarket!")
 print("1. Potatoes (0ドル.75 per potato")
 print("2. Tomatoes (1ドル.25 per tomato")
 print("3. Apples (0ドル.5 per apple")
 print("4. Mangoes (1ドル.75 per mango")
 print("5. Checkout")
 user_choice = int(input())
 if user_choice==1:
 potatoes=int(input("How many potatoes?"))
 total=total+potatoes*0.75
 elif user_choice==2:
 tomatoes=int(input("How many tomatoes?"))
 total=total+tomatoes*1.25
 elif user_choice==3:
 apples=int(input("How many apples?"))
 total=total+apples*0.5
 elif user_choice==4:
 mangoes=int(input("How many mangoes?"))
 total=total+mangoes*1.75
 if user_choice==5:
 print("The total cost is $",total)
 pay=float(input("please enter an amount to pay for the fruits and vegetables: "))
 while pay<total:
 pay=float(input("please enter an amount more than payment: "))
 change=pay-total
 print("your change will be $",change)
 d5 = change // 5
 d1 = (change % 5) // 1
 quarter = ((change % 5) % 1) // 0.25
 dime = (((change % 5) % 1) % 0.25) // 0.1
 nickel = ((((change % 5) % 1) % 0.25) % 0.1) // 0.05
 penny = (((((change % 5) % 1) % 0.25) % 0.1) % 0.05) // 0.01
 print("Give the customer", d5, "5ドル note,", d1, "1ドル note,", quarter, "quarter,", dime, "dime,", nickel,"nickel,", penny, "penny.")
 break

• MooingRawr: also instead of just code dumpping maybe explain yourself on what you did, and what OP did wrong ?
• jjjdada: Thank you! This helps a lot !