Why index starts with Zero instead of One?

Question

Here in Python, when you want to get the first element of a vector, you type vector(0), but when you to choose the first element from the end to the beginning you type vector(-1). So you see it is not symmetric. Why this? What is the benefit of ZERO being the first element in a list?

Matlab for instance is more intuitive. vector(1) is the first element. The way it should be in my humble opinion.

Answer 1

Because it have sense behind the scene for efficiency reasons...
A list of value is stored continuously in memory, each item taking the same size of memory.
When you define the list, you store a reference to it in a variable, and this reference can be considerated as the memory address of the first element.
So, when you want to access to the n-th element, you need to know it specific memory address, and the computation to be done is:

address_of_item_n = adress_of_list + (n*size_of_one_item)

... when indexes start at zero.
Else, with indexes starting at 1, the formula becomes:

address_of_item_n = adress_of_list + ( (n-1) * size_of_one_item)

Anyway, to clarify this concept, think about indexes as floor of a building: ground floor is floor number 0, and floor number 1 is not the first element wich fit to live ;)

Answer 2

because at the core arrays are memory addresses. So memory location 0 holds the value of index 0.then the next location stores the next value of index.

index is the distance from first character.
using this you can dereference it easily.

Answer 3

understood. i was just complaining cos I m used to 1 instead of zero, and I also like symmetry. other thing that bothers me a bit is the fact that when you type a[0:3] you get the first element but not the last. it is the one before the last. I dont like that either but what the hell....

thanks anyway