16. EXT: nested for-loops using the range function

16.1. Set pixels

Turning on and off pixels is explained at https://pc-microbit-micropython.readthedocs.io/en/latest/images/setting_pixels.html

Read the above examples before reading further to see how they illustrate nested loops.

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16.2. Using pixels in nested for-loops

In the code below, the outer loop iterates over x values from 0 to 4.

For each x value, the inner loop iterates over y values from 0 to 4.

So when x is 0, y goes from 0 to 4, turning on each pixel in the first column.

This repeats for the other columns.

from microbit import *

for x in range(5):
    for y in range(5):
        display.set_pixel(x, y, 9)
        sleep(100)

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Tasks

1. Write code that turns on the pixels one row at a time from the top.

2. Write code that turns on the pixels one row at a time from the bottom.

Q1

Write code that turns on the pixels one row at a time from the top.

from microbit import *

for y in range(5):
    for x in range(5):
        display.set_pixel(x, y, 9)
        sleep(100)

Q2

Write code that turns on the pixels one row at a time from the bottom.

from microbit import *

for y in range(4,-1,-1):
    for x in range(5):
        display.set_pixel(x, y, 9)
        sleep(100)

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16.3. Advanced: nested for-loops with range function

What does this code do?

What are the values of startnum in the nested loop?

from microbit import *

while True:
    for startnum in range(4):
        for n in range(startnum, startnum + 5, 2):
            display.scroll(n, delay=40)