Variables and types #

Imagine you're writing a program that greets a user by name. You need somewhere to keep that name so you can use it. Or maybe you're tracking a score in a game — the number needs to live somewhere while the program runs.

That's what a variable does. It's a named place to store a piece of information.

Saving a value #

You create a variable by writing a name, then =, then the value you want to store:

name = "Alice"

After this line runs, Python remembers that name holds "Alice". You can then use name anywhere in your code and Python will substitute the value in.

print(name)
# Alice

One thing that trips people up early: that = sign doesn't mean "is equal to" like in maths. It means store this value in this name. You're not asking a question — you're giving an instruction. Read it as "name gets Alice".

Picking a good name #

You get to choose the name. The key is to make it describe what it holds — code is read far more than it's written, so clear names save you confusion later.

favourite_colour = "blue"
age = 25
city = "Melbourne"

A few rules Python enforces:

• No spaces — use underscores instead: first_name not first name
• Start with a letter — score2 is fine, 2score isn't
• Case matters — Name and name are two completely different variables

And one convention the Python community follows (not enforced, just expected):

• Use lowercase with underscores: user_name, total_price, is_active

Four kinds of values #

Python treats different kinds of information differently. Here are the four you'll use all the time.

Text #

Any text value goes inside quote marks:

greeting = "Hello!"
country = "Australia"
message = "See you tomorrow"

The quotes are how Python tells the difference between text and code. Without them, Python would think Hello was the name of a variable, not the word hello. You can use single or double quotes — they behave identically, so pick one and be consistent.

This kind of value has a name in programming: a string. You'll hear that term a lot.

Numbers #

Numbers don't get quotes:

age = 28
year = 2024
price = 4.99
discount = 0.15

There are two flavours. Integers are whole numbers — no decimal point. Floats are numbers with a decimal point. Python handles them slightly differently under the hood, but for now just know: if you need decimals, use a decimal point.

True or False #

Some information is simply one of two states — on or off, yes or no:

is_logged_in = True
has_paid = False
is_available = True

These are called booleans and they're incredibly useful. A lot of decisions in code come down to "is this true or not?" Notice they're capitalised: True and False, not true and false.

Nothing #

Sometimes you want to say "this variable exists, but there's no value in it yet":

result = None
winner = None

None is Python's way of representing the absence of a value. It's not zero, it's not empty text — it's genuinely nothing. You'll often use it as a placeholder before you have a real value to store.

Updating a variable #

Variables aren't fixed. You can give them a new value any time:

score = 0
print(score)  # 0

score = 10
print(score)  # 10

score = score + 5
print(score)  # 15

Each time you use =, the old value is replaced. That last line is worth reading carefully: score = score + 5 means "take the current value of score, add 5 to it, and store that as the new score". It looks circular but it's perfectly valid — the right side is calculated first, then stored.

Putting variables to work #

Variables become powerful when you use them together:

first_name = "Alice"
last_name = "Smith"
full_name = first_name + " " + last_name

print(full_name)
# Alice Smith

price = 12.00
quantity = 3
total = price * quantity

print(total)
# 36.0

This is the core idea: store values, name them clearly, then use those names to do something useful.

Quick reference #

Practice #