Functions

Functions are snippets of code that can be reused.

functions.py

def get_menu_option():
    option = input(f'${balance} A)dd Money  S)ubtract Money Q)uit:')
    return option

def get_money():
    money = input('Enter amount:')
    return int(money)

def add_money():
    # you need access to the global balance
    global balance
    
    print('Add money')
    money = get_money()
    balance = balance + money

def subtract_money():
    # you need access to the global balance
    global balance
    
    print('Subtract money')
    money = get_money()
    balance = balance - money

def invalid_option():
    print('Invalid option, try again')
    
balance = 0

# do the while loop forever
while True:
    option = get_menu_option()

    match option:
        case 'a':
            add_money()
        case 's':
            subtract_money()
        case 'q':
            # exit the while loop
            break
        case default:
            invalid_option()

print("Done.")

Output:

$0 A)dd Money  S)ubtract Money Q)uit:a
Add money
Enter amount:10
$10 A)dd Money  S)ubtract Money Q)uit:s
Subtract money
Enter amount:20
$-10 A)dd Money  S)ubtract Money Q)uit:a
Add money    
Enter amount:30
$20 A)dd Money  S)ubtract Money Q)uit:q
Done.

The balance variable needs to be marked as global inside functions so that it can update it. If you don't do this then you will get an error.

Links

• Python Arrays

Exercises (5 mins)

1. Create functions for each of the case statements.

   find_a_number.py

   # create get_menu_option
   
   # create add_pet function
   
   # create remove_pet function
   
   # create list_all_pets function
   
   list_of_pets = []
   
   # do the while loop forever
   while True:
       option = input(f'{len(list_of_pets)} A)dd Pet  R)emove Pet  L)ist pets Q)uit:')
   
       match option:
           case 'a':
               pet_name = input('Enter pet name to add:')
               list_of_pets.append(pet_name)
           case 'r':
               pet_name = input('Enter pet name to remove:')
               list_of_pets.remove(pet_name)
           case 'l':
               for pet in list_of_pets:
                   print(pet)
           case 'q':
               # exit the while loop
               break
           case default:
               print('Invalid option, try again')
   

   Output:

   0 A)dd Pet  R)emove Pet  L)ist pets Q)uit:a
   Enter pet name to add: tootsie
   
   1 A)dd Pet  R)emove Pet  L)ist pets Q)uit:a
   Enter pet name to add: fido
   
   2 A)dd Pet  R)emove Pet  L)ist pets Q)uit:l
   tootsie
   fido
   
   2 A)dd Pet  R)emove Pet  L)ist pets Q)uit:r
   Enter pet name to remove: fido
   
   1 A)dd Pet  R)emove Pet  L)ist pets Q)uit:q
   
   Done.