In Python, how can I change the sign of one number in a list based on another number's sign?

I have two values in a list, let's say it's ``` A = [1, -3] ``` If the sign of the second value is positive, I can leave the number alone. If the sign of the second value is negative, I need to change the first value to be a -1. But if the first value is a 0, nothin needs to be done at all, since -0 is the same as a positive zero. So in the case of A, I would need to change 1 to -1. So the final result should be ``` A = [-1, -3] ``` I'm a new programmer, so basically all I think is that it involves appending a value to the end of A, and then removing the first value. I think we have to do that because as far as I know, there's no way of just changing the sign of a number. So, I think it might be something like this: ``` A = [1, -3] for i in A: if #something about the second value being a positive value pass else: A.append("-1") del A[0] print A ``` Any help would be appreciated, thanks!