array.index dont print number

Question

I have a problem with return even index in array.

def checkio(array):
if len(array):
    return ([i for i in array if array.index(i) % 2 == 0])
else:
    return 0

print (checkio([-37,-36,-19,-99,29,20,3,-7,-64,84,36,62,26,-76,55,-24,84,49,-65,41]))

and this code return

[-37, -19, 29, 3, -64, 36, 26, 55, -65]

but if i change '84' in my array for example for '74' its return

[-37, -19, 29, 3, -64, 36, 26, 55, 74, -65]

What the problem is it?

NPE · Accepted Answer · 2014-09-17 08:25:57Z

1

The issue is that 84 appears twice:

print (checkio([-37,-36,-19,-99,29,20,3,-7,-64,84,36,62,26,-76,55,-24,84,49,-65,41]))
                                               ^^                     ^^

However, array.index() returns the index of the first occurrence. This happens to be at an odd index so all occurrences of 84 get suppressed.

If you just want to take every other element, simply write array[::2]. This will take elements at indices 0, 2, 4, etc. No need to do any lookups.

answered Sep 17, 2014 at 8:25

NPE

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