🔒 How to obtain the first element on a list with reverse slice?

[hoary bronze]

How to obtain the first element in a list when I am using the (reversed) slice object.

I want to return 10 from the list when using [::-1] slice type object.

x = [10, 20, 30, 40] 
x[1:0:-1] # returns 20
x[1:-1:-1] # Does not return 10
x[0::-1] # Note: I can't use it since I am decrementing a variable here

[lofty geode]

@hoary bronze

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[devout ingot]

maybe you mean x[-1], which selects the last element from the list

[cursive cedar]

i assume you mean that you want to slice out a list with a single element containing the first element

you'll need to elaborate on what you mean by I can't use it since I am decrementing a variable here

[hoary bronze]

I need to retain the slice format

[devout ingot]

why?

[austere tangle]

[::-1][-1]

[cursive cedar]

what are you actually trying to do here?

[hoary bronze]

It is in a loop where I am changing the 2nd variable in the slice object.

[cursive cedar]

what is the loop for?

[austere tangle]

Maybe just share your code

[steel sundial]

probably overcomplicating it

[austere tangle]

That's what I'm thinking

[cursive cedar]

it's possible that you will just have to make it a special case in the end

the way indices jump from 0 to -1 in python is a common special case

[hoary bronze]

I've suspected that, and trying to confirm it.

@austere tangle Code won't add more to my question.

x = [10, 20, 30, 40]

for i in range(len(x)):
    print(x[i:i-1:-1])

# OUTPUT
#[] # Missing
#[20]
#[30]
#[40]

The question is if slice operator can do fetch the missing item.

[devout ingot]

is there any reason you need it to be done with a -1 slice? why can't you just print(x[i])?

[hoary bronze]

There is.

[austere tangle]

Hmm. From the code you shared there really isn't though

Can you share your actual code?

[austere tangle]

There's still my original answer too

[devout ingot]

what is that reason?

and -- why can't you use x[0::-1]? that gives you what you want

[hoary bronze]

because the code is in a x[variable:variable:-1] format.

[devout ingot]

but it doesn't have to be, no?

[hoary bronze]

Thanks for trying. I'll close it now.

!close

[lofty geode]

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