Python Tuple Slicing

Question

Given that -1 goes back to the first term in a tuple, and the end index of a slice stops before that index, why does

x=(1,2,3,4,5)
x[0:-1]

yield

(1, 2, 3, 4)

instead of stopping at the index before the first which is 5?

Thanks

[This question has been answered before and very thoroughly.](http://stackoverflow.com/questions/509211/pythons-slice-notation) — , Jan 15 '14 at 04:41

score 14 · Accepted Answer · answered Jan 15 '14 at 03:58

14

-1 does not go back to the first term in a tuple

x=(1,2,3,4,5)
x[-1]

yields

answered Jan 15 '14 at 03:58

twj

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score 10 · Answer 2 · answered Jan 15 '14 at 04:43

10

It helps to think of the slicing points as between the elements

x = (   1,   2,   3,   4,   5   )
      |    |    |    |    |    |
      0    1    2    3    4    5
     -5   -4   -3   -2   -1

answered Jan 15 '14 at 04:43

John La Rooy

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You could also say that the end index is non-inclusive. – Wayne Weibel Dec 01 '15 at 18:56

score 5 · Answer 3 · answered Jan 15 '14 at 03:58

5

Slicing works like this:

x[start : end : step]

In your example, start = 0, so it will start from the beginning, end = -1 it means that the end will be the last element of the tuple (not the first). You are not specifying step so it will its default value 1.

This link from Python docs may be helpful, there are some examples of slicing.

answered Jan 15 '14 at 03:58

Christian Tapia

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1

the `end` in `x[start : end : step]` would not be in the slice result. – Shihe Zhang Nov 21 '18 at 03:03

score 0 · Answer 4 · edited Mar 07 '16 at 03:56

0

A -ve value in any python sequences means :

Val = len(sequence)+(-ve value)

Either start/stop from/to len(sequence)+(-ve value), depending on what we specify.

edited Mar 07 '16 at 03:56

ketan

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answered Mar 07 '16 at 03:39

aady

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Python Tuple Slicing

4 Answers4