Confused with python lists challenge question

Question

What is the output of this code?
squares = [0, 1, 4, 9, 16, 25, 36]
print(squares [1:1:-1])

Solution : []

My answer was [1] on account that the first index of a slice is included but it seems thats wrong here.Can someone explain this to me?

Answer 1

brigx well, HonFu point was right.
You can revise the lesson of slicing you will see that in [x,y] the y will never be printed simply because it's a range starting from 0.
Just imagine a code with this command: print this list starting from index 1 but at the same time don't include index 1

Answer 2

In list slicing there are usually 3 factors, [x:y:z]
The x starts the slice, y ends it but doesn't get involved in the action, z is the steps that x will take to go to y, if 1 then it will take 1 step as normal, if -1 then it will be reversed

The statement says print(squares[1:1:-1]
So it will print from 1 to 1 taking a step to the back [-1], it doesn't make any sense, Python will output an empy list as you can't move from a number to the same number and even with negative step.

I hope what i'm saying makes sense

Answer 3

The ending value of a range is not included. A range of 5 goes from 0 to 4, a range of 1 has only 0 in it.

And a range/slice that goes from 1 to 1, not including the last element, effectively contains nothing.

Answer 4

Mo Hani thank you i really never asked myself why for the slice [x:y] y is not in the values it makes sense now if the index starts at 0 thanks HonFu you were right all along

Answer 5

I have to disagree with you HonFu the lesson on lists says the first index in a slice i.e x in [x:y] is included in the results so applying that same logic to the above question would value 1 at index 1 not be included in the slice?.I get the part where -1 means reversing the slice its just that the solution seems contradictory to the lesson....or im being thick headed 😂

Answer 6

Hi

Answer 7

I have a problem. Who can help me?

Answer 8

https://code.sololearn.com/cAWpY5aC73ij/?ref=app

Answer 9

Where is the problem with this code?
Why is not the output correct?

Answer 10

reza what do you mean by output not correct

Answer 11

brigx
For example, why when I enter 8, the message (you are child) is not displayed?

Answer 12

reza Please ask your question in a separate thread.

Answer 13

reza dont nest the ifs and their statements it should work just fine