this solution will break if you pass as input not a string but a int

This really helped me too! Thank you!

Python strings can be repeated using the * operator. Here, "#" is repeated to match the length of the masked portion of cc. Check out the Python tutorial.

What does the * do in this case? Thank you!

Thanks.

Note that returning any positive number from the comparison function is the same as returning 1, so you can shorten it to a - b. Also, slice() can use negative indices so ages.length - 2 is equivalent to -2, and end defaults to the length of the array, so ages.length is redundant.