Question

This what I have so far. It’s for homework. We can’t use slices. I can’t seem to figure it out.

def insert(s1, s2, pos):
    s3 = list(s1)
    for i,s in enumerate(s3):
        if i == pos:
            s3[pos + 1] = s
            s3[i] = s2
    "".join(s3)     
    return s3

With the above, the last character of string s1 gets deleted and the join method is not joining s3 into a single string.

Answer 1

Notice the lines

"".join(s3)     
return s3

If you look at the join documentation, you’ll see that join doesn’t modify its argument, but instead generates a string containing the contents of the argument list, all joined together. So you’re throwing away the result of

"".join(s3)

and returning s3 (a list) instead. So, you need to change the last two lines to

return ''.join(s3)

Since this is homework, I won’t comment on the rest of the code, but returning the result of the join call will certainly help.