I feel like an idiot for asking this but why is it ndx +1 for range instead of just ndx?

The answer is to divide by 2, if the remainder is 1, then it is odd, and if the remainder is 0, it is even

It's too coooool!

As I know, at first, possible errors, non-standard situations are written in the if block.

I don't even get this solution but I'm new to this. How do we decide which are odd-numbers and which are even?

Wow I didn't think of that

I agree, although I would never get to the mathematical formula, as I'm not a mathematical person, but there is a massive difference between running the function with a considerably high "m" number
when your solution solves it instantly.

Very interesting the always problematic execution time :)

If I understood correctly, a modified list should have been returned.

When calling decrypt("This is a test!", 1), it outputs " Tah itse sits!", but the output should be "hsi etTi sats!".

lolz

nice

It's clever, but I think you could exclude the "else" from the statement, since "return" ends the function execution.
It would increase readability.