Variables allow us to store data during our program’s execution. Sometimes, variables are described as containers for storing information. For example, in an RPG video game, your character has attributes such as health, magic, and stamina. These values need to be tracked throughout the game. Variables enable us to store and use this data within the program.
You use the equal sign (=) to assign a value to a variable. Here, you can both declare and assign a value in one line, which is known as initialization. Python handles data types like strings, integers, and floats seamlessly. Python uses dynamic typing, which means the data type a variable stores can change during runtime.
# Assign a string value to a variable
name = "Anthony"
# Initialize an integer and a float variable
age = 5
weight = 500.55
name = 10 # This will overwrite the previous value, Python is flexible like that
Variables can be used anywhere their given data type may be used.
number1 = 10
number2 = 400
sum = number1 + number2
print(f"The sum is {sum}")
Example Video
Variable scope refers to where a variable can be accessed in your code. For example, the program below will raise an error because number1 must be declared before it can be used.
# Error
print(number1)
number1 = 5
There are some syntax rules for naming variables, and there are best practices known as conventions. Here are a few tips for naming variables:
age = 25 is more descriptive than x = 25 if the variable is storing an age value.snake_case when naming a variable containing multiple words.# String variables
print("- String variables -")
# Declare string variables
name = "Anthony" # Try using your name instead of mine
food = "Steak" # Try replacing steak with your favorite food.
item = "peppers" # Try replacing this with some other noun.
print(f"Hello, this is {name}!")
print(f"{name} loves to eat {food}.")
print()
print("Try saying this five times fast:")
print(f"Peter Piper picked a peck of pickled {item}")
print(f"A peck of pickled {item} Peter Piper picked")
print(f"If Peter Piper picked a peck of {item},")
print(f"Where’s the peck of {item} Peter Piper picked?")
print()
# Number variables
print("- Number variables -")
age = 30 # Replace the number with your age
print(f"You will reach age 100 in {100 - age} years!")
print()
balance = 35.25
withdraw = 0 # Replace the 0 with a larger number.
leftover = balance - withdraw
print(f"You have a balance of ${balance} in your bank account.")
print(f"If you withdraw ${withdraw}, you will have ${leftover}.")
print()
health = 100
damage = 55.5
print(f"You've taken {damage} damage. You have {health - damage} health left.")
- String variables -
Hello, this is Anthony!
Anthony loves to eat Steak.
Try saying this five times fast:
Peter Piper picked a peck of pickled peppers
A peck of pickled peppers Peter Piper picked
If Peter Piper picked a peck of peppers,
Where's the peck of peppers Peter Piper picked?
- Number variables -
You will reach age 100 in 70 years!
You have a balance of $35.25 in your bank account.
If you withdraw $0, you will have $35.25.
You've taken 55.5 damage. You have 44.5 health left.
print() in Python does not always need a string argument. For example, don’t write print(f"{number_variable}") when print(number_variable) will suffice.