Personally whether I feel I should apologize for a bug in my code depends on a lot of things. If it's a bug in some code that I've made open to others then the

Personally whether I feel I should apologize for a bug in my code depends on a lot of things. If it's a bug in some code that I've made open to others then the code normally comes with instructions telling them what to do when they find a bug, that in itself implies there are going to be bugs in the code and so I don't feel the need to apologize for it (note I usually do thank people when they report a bug, doubly so if they include a fix!). If it's a bug in some code at work where a more junior developer has spent a day struggling with it before figuring out that it's not their code that's wrong, then I might apologize. Not a grovelling apology begging for forgiveness, but more of casual acknowledgement that I made a mistake in the code. Acknowledging that the issue wasn't in their code is important. Also I use the apology as a way to give them permission to fix the code they haven't written - once they're more experienced they won't need this, but when they're starting out realizing that other developers make mistakes and that you can fix them is important.