Lesson 2 — Variables and Data Types

Estimated time: 60 minutes

Learning Objectives

By the end of this lesson you will be able to:

  1. Create variables to store values
  2. Identify and use the four basic data types: int, float, bool, str
  3. Use type() to check what type a value is
  4. Use variables to control the NeoPixel colour

Concepts

What is a Variable?

A variable is a named storage location in your program’s memory. Think of it as a labelled jar — the label is the variable name, and the contents are the value stored inside.

score = 0          # A jar labelled "score" containing the number 0
player_name = "Alex"   # A jar labelled "player_name" containing "Alex"

You create a variable by writing its name, then =, then the value. The = is called the assignment operator — it puts the value into the variable.

You can then use the variable name anywhere you’d use the value:

score = 42
print(score)        # Prints: 42
print(score + 10)   # Prints: 52

Variable naming rules:

  • Must start with a letter or underscore (not a number)
  • Can contain letters, numbers, and underscores
  • Case-sensitive: Score and score are different variables!
  • No spaces: use player_name not player name
  • Good names: score, led_brightness, is_running, sensor_value
  • Bad names: 2score, my variable, s@core

The Four Basic Data Types

Python has four basic data types — categories of value:

int — Integer

Whole numbers. No decimal point. Can be positive, negative, or zero.

score = 0
lives = 3
year = 2025
temperature = -5
max_brightness = 255

float — Floating Point Number

Numbers with a decimal point.

pi = 3.14159
temperature = 36.6
distance = 23.4
percentage = 87.5

bool — Boolean

Only two possible values: True or False (capital T/F required!). Used for yes/no decisions.

game_over = False
light_is_on = True
player_is_alive = True

str — String

Text — any sequence of characters, enclosed in single or double quotes.

player_name = "Alex"
greeting = "Hello!"
colour = 'red'
message = "The score is 42"   # Even if it contains a number, it's text

Notice: 42 is an int (the number forty-two), but "42" is a str (the text “42”). They look similar but behave completely differently! You can do maths with 42 but not with "42".

Checking the Type

Use type() to check what type a value or variable is:

print(type(42))         # <class 'int'>
print(type(3.14))       # <class 'float'>
print(type(True))       # <class 'bool'>
print(type("hello"))    # <class 'str'>

Updating Variables

You can change what’s in a variable at any time:

score = 0
print(score)    # 0

score = 10
print(score)    # 10

score = score + 5    # Take the current value, add 5, store result back
print(score)    # 15

Guided Walkthrough

Step 1: Creating Variables

Type this in the Script Editor and run it:

# Integer variables
score = 0
lives = 3
year = 2025

# Float variables
temperature = 36.6
pi = 3.14159

# Boolean variables
game_over = False
light_is_on = True

# String variables
player_name = "Alex"
favourite_colour = "blue"

# Print them all
print("Score:", score)
print("Lives:", lives)
print("Temperature:", temperature)
print("Game over?", game_over)
print("Player name:", player_name)

Step 2: Checking Types

Try these in the REPL:

>>> print(type(42))
<class 'int'>
>>> print(type(3.14))
<class 'float'>
>>> print(type(True))
<class 'bool'>
>>> print(type("hello"))
<class 'str'>
>>> x = 100
>>> print(type(x))
<class 'int'>

Step 3: Variables with the NeoPixel

This is where variables become genuinely useful. Instead of hardcoding numbers, use variables:

import machine
import neopixel
import time

pin = machine.Pin(48, machine.Pin.OUT)
np = neopixel.NeoPixel(pin, 1)

# Store the colour components in variables
red_value = 200
green_value = 0
blue_value = 150

np[0] = (red_value, green_value, blue_value)
np.write()
print("LED colour set!")
print("Red:", red_value)
print("Green:", green_value)
print("Blue:", blue_value)

time.sleep(3)
np[0] = (0, 0, 0)
np.write()

Try changing red_value, green_value, blue_value and re-running. Notice how much easier it is to adjust the colour when it’s stored in named variables.

Step 4: Updating Variables — Brightness Fade

Here’s a more advanced example that updates a variable inside a loop to create a fading effect:

import machine
import neopixel
import time

pin = machine.Pin(48, machine.Pin.OUT)
np = neopixel.NeoPixel(pin, 1)

# Start with brightness 0 and increase to 255 in steps
brightness = 0

# This is a loop (we'll cover loops properly in Unit 3)
# For now, just notice that brightness changes each iteration
for step in range(11):
    brightness = step * 25          # 0, 25, 50, 75, ... 250
    np[0] = (brightness, 0, 0)      # Red, getting brighter
    np.write()
    print("Brightness:", brightness)
    time.sleep(0.2)

# Turn off
np[0] = (0, 0, 0)
np.write()
print("Done!")

Challenges

⭐ Core

Create variables for your name, age, and favourite colour. Print a sentence using all three: "My name is [name], I am [age] years old, and my favourite colour is [colour].". Then look up the RGB values for your favourite colour and display it on the LED.

⭐⭐ Extension

Create a boolean variable is_bright = True. Use it to decide whether the LED shows full brightness (255) or dim (40). Then change the variable to False and re-run — the LED should change automatically. Print which mode is active.

⭐⭐⭐ Stretch

Create variables for three different colours (look up RGB values for each). Show each colour for 2 seconds, printing the colour name and its R, G, B values each time. After showing all three, show a “white” for 1 second (hint: white is all three channels at full brightness), then turn off.

Common Mistakes & Debugging

NameError: name 'x' is not defined You used a variable before creating it, or you misspelled the name. Python is case-sensitive: Score and score are completely different.

Using = to compare instead of == = assigns a value. == checks if two things are equal. You’ll use == in Unit 2 when you start making decisions.

Forgetting quotes around strings name = Alex — Python thinks Alex is a variable name. You need name = "Alex".

Variable names with spaces player name = "Alex" is a syntax error. Use underscores: player_name = "Alex".

TypeError when mixing types "My score is " + 42 will fail because you can’t add a string and an integer directly. You’ll learn how to fix this in Lesson 4.

Key Vocabulary

Term Definition
variable A named storage location in memory that holds a value
assignment Giving a variable a value using the = operator
data type The category of a value — int, float, bool, or str
int Integer — a whole number with no decimal point
float Floating-point number — a number with a decimal point
bool Boolean — can only be True or False
str String — a sequence of text characters, written in quotes
type() A built-in function that returns the data type of a value
case-sensitive Uppercase and lowercase letters are treated as different: Score ≠ score

Copyright © Paul Baumgarten.