Some scripts you will write for cybersecurity encryption and decryption will need to access each character in a string.   As a warmup for this, let's try a script that checks and displays a certain character in a string.

Example script: char_access_intro

• Enter, name, and save char_access_intro.  
• Click the Send to micro:bit button.

# char_access_intro

from microbit import *

sleep(1000)

s = "ABCDEF 12345"
 
print("Fifth character in s:")
 
c = s[5]
 
print("c = s[5] =", c)
 
print()

• Check the results in the serial monitor.
• Verify that it displays c = s[5] = F.

• Try replacing 5 with other values, like 0, 1, 2, ...and anything up to 11.  What happens with each value?

How char_access_intro Works

The string s is "ABCDEF 12345".  The string name, followed by a positive index value in square brackets, returns the character at that location in the string.  The index starts with A at s[0], B is at s[1], and so on up to the character 5 at s[11].  You can also use -1 through -12 to index characters from rightmost to left.