Python List Slice

Question

Hey
Can somebody help me please with this question!!

What is the output of this code?
sqs = [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
print(sqs[7:5:-1]

The Answer is: [49, 36]
But why?????

Thanks for your Answers!

Answer 1

-1 = len(array)-1

So you start slicing from the end of the array. The first parameter(7) is included in the slice but the 2nd parameter isn't. So the slice ends at the 6th element.

Answer 2

print(sqs[7:5:-1])

7:5=means start from 7 index and end at 4 index 5 will be not included.here you are going 7 to 5 means backward and you need -1 step for backward index.

that's why output is =
7:5:-1=[49,36]

Answer 3

var[start:when to stop:how to iterate]

sqs[7:5:-1]

-start in element 7 (49)
-stop if we reach element 5 or pass .
- -1 means we add -1 for iterations.

So :
7
6
stop

See? this results printing 7 element and 6 element (49, 36)

Answer 4

Anya LambdaDriver Thanks for your help!!

Answer 5

Maninder Singh Thanks!

Answer 6

can you help me?

Answer 7

what seems to be the problem?

Answer 8

Thanks Anya!
so -1 means that the list is read backwards!?

Answer 9

Nils yes. It's like LambdaDriver said.

Answer 10

No problem Nils