How to assign a new value for a variable in function, Python?

Question

I need to implement some kind of coffee machine. It has initial state of ingridients (WATER = 400; MILK = 540; BEANS = 120; EMPTY_CUPS = 9; MONEY = 550) and can do some actions (BUY = "buy" - buy some coffee(1 - espresso, 2 - latte, 3 - cappuccino); FILL = "fill" - add ingridients; TAKE = "take" - take all earned money; REMAINING = "remaining" - show remaining ingridients; EXIT = "exit"). After buying or filling the amount of ingridients changes. Here is my code

# actions
BUY = "buy"
FILL = "fill"
TAKE = "take"
REMAINING = "remaining"
EXIT = "exit"
# initial supply
WATER = 400
MILK = 540
BEANS = 120
EMPTY_CUPS = 9
MONEY = 550
# coffee
ESPRESSO = "1"
LATTE = "2"
CAPPUCCINO = "3"
water = WATER
milk = MILK
beans = BEANS
cups = EMPTY_CUPS
money = MONEY


def remaining():
    print(f''' The coffee machine has:
 {water} of water
 {milk} of milk
 {beans} of coffee beans
 {cups} of disposable cups
 {money} of money
          ''')


def fill():
    global water, milk, beans, empty_cups, money
    print('Write how many ml of water do you want to add:')
    add_water = int(input())
    print("Write how many ml of milk do you want to add:")
    add_milk = int(input())
    print("Write how many grams of coffee beans do you want to add:")
    add_coffee = int(input())
    print("Write how many disposable cups of coffee do you want to add:")
    add_cups = int(input())
    water = WATER + add_water
    milk = MILK + add_milk
    beans = BEANS + add_coffee
    empty_cups = EMPTY_CUPS + add_cups
    money = MONEY
    return water, milk, beans, empty_cups, money


def take(money):
    print(f"I gave you ${money}")
    water = WATER
    milk = MILK
    beans = BEANS
    empty_cups = EMPTY_CUPS
    money = 0
    return water, milk, beans, empty_cups, money


def buy():
    global water, milk, beans, cups, money
    print('What do you want to buy? 1 - espresso, 2 - latte, 3 - cappuccino:')
    coffee = input()
    if coffee == ESPRESSO:
        water = WATER - 250
        milk = MILK
        beans = BEANS - 16
        cups = EMPTY_CUPS - 1
        money = MONEY + 4

    elif coffee == LATTE:
        water = WATER - 350
        milk = MILK - 75
        beans = BEANS - 20
        cups = EMPTY_CUPS - 1
        money = MONEY + 7
    else:
        water = WATER - 200
        milk = MILK - 100
        beans = BEANS - 12
        cups = EMPTY_CUPS - 1
        money = MONEY + 6
    return water, milk, beans, cups, money


def main():
    remaining()
    while True:
        action = input("Write action (buy, fill, take, remaining, exit):")

        if action == BUY:
            buy()
        elif action == FILL:
            water, milk, beans, cups, money = fill()
        elif action == TAKE:
            water, milk, beans, cups, money = take(MONEY)
        elif action == REMAINING:
            remaining()
        else:
            break


main()

The problem is that the amount of ingridients changes only once. If I call "buy" or "fill" several times, the amount of ingridients changes only once.

Output:

 The coffee machine has:
 400 of water
 540 of milk
 120 of coffee beans
 9 of disposable cups
 550 of money
          
Write action (buy, fill, take, remaining, exit):buy
What do you want to buy? 1 - espresso, 2 - latte, 3 - cappuccino:
1
Write action (buy, fill, take, remaining, exit):remaining
 The coffee machine has:
 150 of water
 540 of milk
 104 of coffee beans
 8 of disposable cups
 554 of money
          
Write action (buy, fill, take, remaining, exit):buy
What do you want to buy? 1 - espresso, 2 - latte, 3 - cappuccino:
1
Write action (buy, fill, take, remaining, exit):remaining
 The coffee machine has:
 150 of water
 540 of milk
 104 of coffee beans
 8 of disposable cups
 554 of money
          
Write action (buy, fill, take, remaining, exit):

I'm new to Python and stuck totally. Could you tell me, please, how can I fix it? I need the amount of ingridients changes after every call of buy/fill.

Answer 1

Modified the code, maybe this is what you wanted:

# actions
BUY = "buy"
FILL = "fill"
TAKE = "take"
REMAINING = "remaining"
EXIT = "exit"
# initial supply
WATER = 400
MILK = 540
BEANS = 120
EMPTY_CUPS = 9
MONEY = 550
# coffee
ESPRESSO = "1"
LATTE = "2"
CAPPUCCINO = "3"
water = WATER
milk = MILK
beans = BEANS
empty_cups = EMPTY_CUPS
money = MONEY


def remaining():
    global water, milk, beans, empty_cups, money
    print(f''' The coffee machine has:
 {water} of water
 {milk} of milk
 {beans} of coffee beans
 {empty_cups} of disposable cups
 {money} of money
          ''')


def fill():
    global water, milk, beans, empty_cups, money
    print('Write how many ml of water do you want to add:')
    add_water = int(input())
    print("Write how many ml of milk do you want to add:")
    add_milk = int(input())
    print("Write how many grams of coffee beans do you want to add:")
    add_coffee = int(input())
    print("Write how many disposable cups of coffee do you want to add:")
    add_cups = int(input())
    water+=add_water
    milk+=add_milk
    beans+=add_coffee
    empty_cups+=add_cups
    return water, milk, beans, empty_cups, money


def take(some_money):
    global water, milk, beans, empty_cups, money
    print(f"I gave you ${some_money}")
    money-=some_money
    return water, milk, beans, empty_cups, money


def buy():
    global water, milk, beans, empty_cups, money
    print('What do you want to buy? 1 - espresso, 2 - latte, 3 - cappuccino:')
    coffee = input()
    if coffee == ESPRESSO:
        water-=250
        milk = milk
        beans-=16
        empty_cups-=1
        money+=4

    elif coffee == LATTE:
        water-=350
        milk-=75
        beans-=20
        empty_cups-=1
        money-=7
    else:
        water-=200
        milk-=100
        beans-=12
        empty_cups-=1
        money+=6
    return water, milk, beans, empty_cups, money


def main():
    remaining()
    while True:
        action = input("Write action (buy, fill, take, remaining, exit):")

        if action == BUY:
            buy()
        elif action == FILL:
            water, milk, beans, cups, money = fill()
        elif action == TAKE:
            water, milk, beans, cups, money = take(MONEY)
        elif action == REMAINING:
            remaining()
        else:
            break


main()