Question about List Slices | Sololearn: Learn to code for FREE!

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Question about List Slices

Hello dear community, Why squares = [0, 1, 4, 9, 16, 25, 36, 49, 64, 81] print(squares[:1:-1]) Output: [81, 64, 49, 36, 25, 16, 9, 4] But squares = [0, 1, 4, 9, 16, 25, 36, 49, 64, 81] print(squares[0:1:-1]) Output: [] Aren’t these print statements equal?

9/22/2022 7:25:33 AM

Ruslan Guliyev

8 Answers

New Answer

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Nope Actually the first one is [-1:1:-1] With a negative step(3rd value) u should go right to left, otherwise the result is empty. The default first value is -1 in this case.

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Ruslan Guliyev defaults: going forward the first value is most left, Going backwards the first value is most right It is straightforward.

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No! print(squares[:1:-1]) identical to this: print(squares[len(squares):1:-1])

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First list: As we know squares[start:end:step] , first list [:1:-1] your list will start in the end because you let the step equal -1 to the index 1 . Is simply equal to squares [len(squares): 1 : -1] the end is not included.

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Oma Falk But why is the first value converted to -1? Is it just a rule that I need to memorize or there is some logic behind it?

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#index: 0, 1, 2, 3... values = [0, 1, 4, 9, 16, 25, 36, 49, 64, 81] #index:-10,-9,-8,-7...

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Oma Falk Solo Thanks a lot for your answers!

0

squares = [0, 1, 4, 9, 16, 25, 36, 49, 64, 81] print(squares[:1:-1]) print(squares[-1:1:-1]) print(squares[len(squares):1:-1])