In programming, variables are used to store data that can be used later in the program. You’ve already learned how to declare and use variables. But one of the most powerful things about variables is that they don’t have to stay the same throughout a program. We can change the value of a variable after it’s been initialized.
Changing the value of a variable allows you to work with dynamic data. For example, a game might change a player’s score every time they earn points, or an app could update a temperature reading when the weather changes.
Let’s say you have a variable that holds your age:
age = 15
In this example, age is a variable, and it currently holds the value 15. But time passes, and you have a birthday, so now your age is 16. You can change the value of the age variable like this:
age = 16
Changing the variable’s value is as simple as assigning a new value.
Sometimes, you will need to modify a variable by adding, subtracting, etc. to it. For example, let’s say you’re making a fighting game and your player takes damage:
health = 100
# Take damage
health = health - 10
This takes the current value of health, subtracts 10, and saves the new result. If you’re thinking of variables from Algebra class, this might seem odd. Remember, variables in programming aren’t exactly the same as those in math class.
Example Video
print("--- Demo 1 - Battle Demo ---")
player_health = 100
player_attack = 25
enemy_health = 100
enemy_attack = 20
potions = 3
print(f"Health: {player_health}")
print(f"Enemy health: {enemy_health}")
print()
print("Player attacks.")
enemy_health = enemy_health - player_attack
print(f"You did {player_attack} damage! Enemy health: {enemy_health}")
print()
print("Enemy attacks.")
player_health = player_health - enemy_attack
print(f"Enemy did {enemy_attack} damage! Player health: {player_health}")
print()
print("Using potion...")
player_health = player_health + 10
potions = potions + 1
print(f"Player health: {player_health}. Potions left: {potions}")
print("\n\n") # What does \n do? Google search 'Python \n'
print("--- Demo 2 - Banking Simulator ---")
account_name = "Checking Account"
balance = 100.50
print(f"{account_name} balance: {balance}")
print(f"Depositing $99.01 to {account_name}")
balance = balance + 99.01
print(f"{account_name} balance: {balance}")
--- Demo 1 - Battle Demo ---
Health: 100
Enemy health: 100
Player attacks.
You did 25 damage! Enemy health: 75
Enemy attacks.
Enemy did 20 damage! Player health: 80
Using potion...
Player health: 90. Potions left: 4
--- Demo 2 - Banking Simulator ---
Checking Account balance: 100.5
Depositing $99.01 to Checking Account
Checking Account balance: 199.51