It was likely intentional. Appending to a list is O(1), so they create the string only once at the end using 'join'. However, concatenating two strings creates a new string each time, which can be a costly operation.

Not sure if it was on purpose, but I believe making "L" a list is less efficient than making it a string.

Variable names evoke sadness

Is it work when rgb(-10, -10, -10)?

Your code us clear. But I think the program description is the result larger than 140. The input is not. Since the input contains many spaces , the input is always larger than the result. So , although input is larger than 140 , the result may not larger than 140. So , your code does not work welll if the input is larger than 140 while the result is not.

Slicing is your friend!