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2. Micro:bit Functions (MicroPython)

2.1 What are Functions?

Functions are a core concept of programming.

Functions allow us to:

  • Group code together
  • Give that code a name
  • Reuse code instead of rewriting it

This makes programs:

  • Easier to read
  • Easier to debug
  • Easier to build in parts

You can think of a function as a mini-program inside your main program.

2.2 Calling a Function

Calling a function means running the code inside it.

We already use built-in functions on the micro:bit, for example:

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from microbit import *

display.scroll("Hello")

Here, display.scroll() is a built-in function.

Functions always use parentheses ().

2.3 Defining a Function

We can create our own functions using def.

Syntax

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def function_name():
    # code to run

Example

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from microbit import *

def small_dance():
    display.show(Image.HAPPY)
    sleep(500)
    display.show(Image.SAD)
    sleep(500)
    display.show(Image.HAPPY)
    sleep(500)

def show_heart():
    display.show(Image.HEART)
    sleep(1000)

# Call the functions
small_dance()
show_heart()
small_dance()

Here we created two functions of our own small_dance and show_heart.
We can then run these as many times as we like by calling them. This is much easier than writing the same code multiple times.

Key Idea

Functions are often used to gather together code that we want to reuse. This makes our program more efficient and easier to read. We write the function once, but can call it many times.

2.4 Parameters (Inputs)

Functions can take inputs called parameters. A parameter is a variable that we pass into the function when we call it. Just like a normal variable we can use it inside the function by calling its name.

This makes them more flexible.

Syntax

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def function_name(parameter1, parameter2):
    # code using parameters

Example

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from microbit import *

def scroll_message(message):
    display.scroll(message)

def flash_icon(icon, delay):
    display.show(icon)
    sleep(delay)
    display.clear()
    sleep(delay)

scroll_message("Hi")
scroll_message("Microbit")

flash_icon(Image.HEART, 500)
flash_icon(Image.SQUARE, 200)

Key Idea

Parameters let you reuse the same function with different values.

2.5 Returning Values (Output)

Functions can send a value back using return.

This allows us to store or use the result.

Example 1: Returning a Value

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from microbit import *

def add_nums(a, b):
    return a + b

result = add_nums(5, 13)
print(result)

display.scroll(result)

Example 2: Custom Function with Return

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from microbit import *

def is_even(number):
    return number % 2 == 0

if is_even(4):
    display.show(Image.YES)
else:
    display.show(Image.NO)

2.6 Summary

Functions help us:

  • Organise code into reusable blocks
  • Avoid repetition
  • Make programs easier to understand

Key Concepts

  • def → define a function
  • () → call a function
  • Parameters → inputs
  • return → output

2.7 Class Activity (demo)

  1. Create a function that:

    • Flashes a heart 3 times

  2. Create a function with a parameter:

    • Display any message passed in

  3. Create a function that:

    • Takes a number and returns double the value

  4. Extension:

    • Use a button press to trigger your function