1.2 Variables

A variable is a name for a value. Instead of typing the same number or word again and again, you store it once and use the name.

Giving a value a name

You assign a value to a variable with =:

age = 12
name = "Sam"
score = 0

The name goes on the left, the value on the right. After that, whenever you use age, Python uses 12.

Rules for variable names

• Use letters, numbers and underscores. Don’t start with a number.
• Good: player_score, high_score, name2
• Avoid: 2nd_place, my-name (use underscore instead of hyphen)

Using variables

You can use variables in print() and in calculations:

favourite_number = 7
print(favourite_number)           # 7
print(favourite_number + 3)       # 10
message = "My favourite number is"
print(message, favourite_number)  # My favourite number is 7

Overwriting

If you assign a new value to the same variable, the old value is replaced:

lives = 3
print(lives)  # 3
lives = 2
print(lives)  # 2

Getting input from the user

You can ask the user to type something with input():

name = input("What is your name? ")
print("Hello,", name)

Whatever they type (until Enter) is stored as a string. If you want a number, you have to convert it: int(input("Enter a number: ")).

Mini project: Store and print

1. Create variables for your favourite number and a short message.
2. Print them together in one sentence.
3. Use input() to ask for their name and then print “Hello, [name]”.

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Next: 1.3 Operators — maths and comparisons.