如何获取变量以保持 Python 的运行总计？

Question

I am trying to get this function take_input to add to the total whenever the function is run. However, I am unable to get the variable daily_expense to accumulate when an expense is added a second time.

def take_input():
    daily_expense = 0
    inp = int(input("How much did you spend?: "))
    daily_expense += inp
    print(f"Total expenses = {daily_expense}")

    while True:
        x = input("Add another expense? Y/N: ").lower()
        if x == "y":
            take_input()
        elif x == "n":
            break
        else:
            print("Please return a valid response")

def start_program():
    start = input("Add expense? Y/N: ").lower()
    if start == "y":
        take_input()

start_program()

Answer 1

This is the working code

def take_input(daily_expense:int):
   
    inp = int(input("How much did you spend?: "))
    daily_expense += inp
    print(f"Total expenses = {daily_expense}")

    while True:
        x = input("Add another expense? Y/N: ").lower()
        if x == "y":
            take_input(daily_expense)
        elif x == "n":
            break
        else:
            print("Please return a valid response")

def start_program():
    daily_expense = 0
    start = input("Add expense? Y/N: ").lower()
    if start == "y":
        take_input(daily_expense)

start_program()

Answer 2

You're currently defining daily_expense inside of the function; which means every time take_input() is called, you are resetting daily_expense to 0.

Instead, you should either define daily_expense outside of the function so it will no longer be reset each time; or you should accumulate it all within the loop and then print the final value, like so:

    def take_input():
        daily_expense = 0

        more_expenses = input("Add expense? Y/N: ").lower()

        while(more_expenses == "y"):
            inp = int(input("How much did you spend?: "))
            daily_expense += inp
            more_expenses = input("Add expense? Y/N: ").lower()

            if(more_expenses == "n"):
                break
            elif(more_expenses == "y"):
                continue
            else:
                print("Please return a valid response")
                more_expenses = input("Add expense? Y/N: ").lower()

        print(f"Total expenses = {daily_expense}")

    def start_program():
        take_input()

    start_program()

Edit: Additional notes:

• Every time this function is called, the value resets again and reaccumulates.

• If you want to store this value in a database, then I recommend returning it and then using the returned value to update a database entry like so:

   def take_input(): daily_expense = 0 more_expenses = input("Add expense? Y/N: ").lower() while(more_expenses == "y"): inp = int(input("How much did you spend?: ")) daily_expense += inp more_expenses = input("Add expense? Y/N: ").lower() if(more_expenses == "n"): break elif(more_expenses == "y"): continue else: print("Please return a valid response") more_expenses = input("Add expense? Y/N: ").lower() print(f"Total expenses = {daily_expense}") return daily_expense def start_program(): save_this_number_to_db = take_input() # store save this number into database start_program()

Answer 3

Use a while loop instead of recursion to continually process user input.

def start_program():
    daily_expense = 0
    extra = ""
    while 1:
        x = input(f"Add {extra}expense? Y/N: ").lower()
        if x == "y":
            inp = int(input("How much did you spend?: "))
            daily_expense += inp
            print(f"Total expenses = {daily_expense}")
            extra = "another "
        elif x == "n":
            break
        else:
            print("Please return a valid response")