2. Letter chooser

The letter choose follows a similar coding structure as the number chooser.

The main difference is that the letters are chosen from a list, so list indexing is needed.

2.1. Letter chooser: simple version

The code below, sets a variable, char_index, to a starting number, 2.
It then displays the character with index 2 in the list, chars.
When the A-button is pressed, char_index is increased by 1.
To make sure char_index doesn’t just keep increasing without limit, if it has reached 4 when the A-button is pressed, it is reset to 0.

from microbit import *

chars = ["A", "B", "C", "D", "E"]

char_index = 2
display.show(chars[char_index])
while True:
    if button_a.is_pressed():
        char_index += 1
        if char_index > 4:
            char_index = 0
        display.show(chars[char_index])
    sleep(200)

2.2. Letter chooser: by function

The code below chooses a letter from a list of letters.
In the main while-loop, select_char is called to choose a letter, letter, which is then displayed.
The function, select_char( starts the variable, char_index, at the middle index position of the chars list. The middle_index is previously calculated by halving the length of the chars list. middle_index = int(max_char_index / 2)
The while-loop keeps running until the B-button is pressed, then chars[char_index] is returned.
In the while-loop, button-A pressing is used to increase the variable, char_index, until it gets to its biggest allowed value, max_char_index, then it restarts at 0.

from microbit import *

chars = ["A", "B", "C", "D", "E"]
max_char_index = len(chars) - 1
middle_index = int(max_char_index / 2)


def select_char():
    char_index = middle_index
    display.show(chars[char_index])
    while button_b.was_pressed() is False:
        if button_a.is_pressed():
            char_index += 1
            if char_index > max_char_index:
                char_index = 0
            display.show(chars[char_index])
        sleep(200)
    return chars[char_index]


while True:
    letter = select_char()
    display.scroll(letter)
    sleep(200)

Tasks

Add the parameter start_char parameter to select_char, so it looks like: select_char(start_char). Use the index method to get the corresponding index for the letter.