Comments should not duplicate the code (D.R.Y)

Your comments should be D.R.Y. The acronym stands for the programming maxim “Don’t Repeat Yourself.” This means that your code should have little to no redundancy. You don’t need to comment a piece of code that sufficiently explains itself. For example:

return a # Returns a

We can clearly see that 'a' is returned, so there’s no need to explicitly state this in a comment. It adds no information whatsoever and incurs a maintenance cost. This makes comments W.E.T., meaning you “wrote everything twice.”