> or wrap the index to a valid one (like Python)?

Python doesn't wrap indices to a valid one. However, it does allow for negative indices which are shorthand for the length of the list plus that negative index.

  >>> a = [1, 2, 3]
  >>> a[3]
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  IndexError: list index out of range
  >>> a[-1]
  3
  >>> a[-3]
  1
  >>> a[-4]
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  IndexError: list index out of range