punctuation - Should a comma come before 'you' in this sentence?

I'm wondering whether a comma should precede the pronoun 'you' in the sentence examples below:

1. That's not how the computer works, you fool.




2. Thanks for the assignment tips, you saviour.

Whenever I usually write, I always place a comma before the pronoun in sentences like the examples above. However, I haven't really found anything that corroborates the notion that this is 'correct practice'. It is just something I have seen and copied. It would be helpful if someone can correct or explain this to me.

Any responses are much appreciated.

P.S. As an extra piece of help, is the pronoun 'you' an object in the first sentence and a subject in the second sentence? Is it an object pronoun in both? Thanks in advance for any responses to this as well.