I haven't programmed in quite a while but here is a working code.
You start of with setting 2 variables as the first 2 numbers of the fibonacci sequence,they are gonna be the numbers a and b here, then you enter the for loop that will be done n times. So the idea for the sequence is pretty simple, you first save the last 2 fibonacci numbers in the variables c and d and their sum will be next fibonacci number. After that you just update the previous 2 numbers and repeat. Hope it helps.
Edit: just noticed you asked for python lol. But I think you get the idea here.