list1 = [1,2,3,4] If I have list1 as shown above, the index of the last value is 3, but is there a way that if I say list1[4], it would become list1[0]?
3 Answers
You can you modulo math like:
Code:
list1 = [1, 2, 3, 4] print(list1[4 % len(list1)]) Results:
1 Comments
In the situation you described, I myself use the method @StephenRauch suggested. But given that you added cycle as a tag, you might want to know there exists such a thing as itertools.cycle.
It returns an iterator for you to loop forever over an iterable in a cyclic manner. I don't know your original problem, but you might find it useful.
import itertools for i in itertools.cycle([1, 2, 3]): # Do something # 1, 2, 3, 1, 2, 3, 1, 2, 3, ... Be careful with the exit conditions though, you might find yourself in an endless loop.
Comments
You could implement your own class that does this.
class CyclicList(list): def __getitem__(self, index): index = index % len(self) if isinstance(index, int) else index return super().__getitem__(index) cyclic_list = CyclicList([1, 2, 3, 4]) cyclic_list[4] # 1 In particular this will preserve all other behaviours of list such as slicing.
list[-1].