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

Something with list comprehension could work.

A = [1,1,2,3,4]
A = [A[i] + (0 if (i%2 == 0) else .1) for i in range(len(A))]

Just quick and dirty with a ternary. Might not work in your version of Python, can't remember which versions it works with.

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Checked in Python 2.7.3 and Python 3.2.3, output is the same:

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

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

>>> A = [A[i] + (0 if (i%2 == 0) else .1) for i in range(len(A))]

>>> A
[1, 1.1, 2, 3.1, 4]