Python insert vs Ruby insert

Question

Python and Ruby all have the insert method.

Python:

>>> a=[1,2,3,4,5]
>>> a.insert(0, 0)
>>> a
[0, 1, 2, 3, 4, 5]

Ruby:

a=[1,2,3,4,5]
# => [1, 2, 3, 4, 5]
a.insert(0,0)
# => [0, 1, 2, 3, 4, 5]

They have the same effect, but if give negative index, the result is different.

Python:

>>> a=[1,2,3,4,5]
>>> a.insert(-1, 6)
>>> a
[1, 2, 3, 4, 6, 5]

Ruby:

a=[1,2,3,4,5]
# => [1, 2, 3, 4, 5]
a.insert(-1, 6)
# => [1, 2, 3, 4, 5, 6]

Why there is this differences? How to understand?

Answer 1

in the python : insert(x, val), it means insert to the location before x.

so, a.insert(-1, 6)-> put the 6 before -1(location)

in the ruby : it means insert to this location x.

so, a.insert(-1, 6)-> put the 6 at -1.

Answer 2

In Python, the new object is inserted before the element of that certain index. Given an insertion point of 0, a new element is inserted before the item at index 0, which results in the inserted item becoming first. Given an insertion point of -1, a new element is inserted before the last item, so it becomes the second-to-last element.

If you want to insert something to the end of a Python list, simply use append().