add a number to all odd or even indexed elements in numpy array without loops

Question

Lets say your numpy array is:

 A =    [1,1,2,3,4]

You can simply do:

A + .1

to add a number to tha

Answer 1

If the list didn't start with two 1 and you wanted to add to all even numbers, you could use:

A[1::2] += 0.1

or

A[::-2][::-1] += 0.1

In the latter case, [::-1] is used to reverse the array back to normal order.