Why are invariants important in Computer Science

I understand ‘invariant’ in its literal sense. I also recognize them when I type code. But I don’t think I understand the importance of this term in the context of computer science.

Loop invariant vs Assertions

I have an exam on Programming Concepts this Saturday and I am struggling to find some information to understand some concepts better.

Loop Invariants in Python

I have a bit of experience with loop invariants but I’m not really clear on them. I’m trying to learn them through an example in Python. Can someone point one out or help me understand?