How to slice list left and right, except middle part?

Question

List:

x = [1, 6, 2, 7, 1, 6, 1]

len(x)
> 7

How would I split the list for the first 3 and last 3, thus value 7 is left alone using list slicing methods?

Output

x[0:2,4:6] #<-- This doesn't work
> [1, 6, 2, 1, 6, 1] #<-- Expected output

@kantal Is there a way to just keep it same brackets? `x[...,...]` similar to this one? — Chipmunkafy, Dec 08 '18 at 06:36
I just noticed @kantal's concatenation and `del` solutions above. It doesn't get better than that. — Andras Deak -- Слава Україні, Dec 08 '18 at 07:10

b-fg · Accepted Answer · 2018-12-08T10:29:52.543

-1

Meeting OP requeriment: "Is there a way to just keep it same brackets? x[...,...] similar to this one? " (not just using x[:3]+x[-3:]):

Use numpy.delete together with numpy.r_. Specify which first number of elements n1 and which last number of elements n2 you want to keep this way

import numpy as np
x = [1, 6, 2, 7, 1, 6, 1]
n1 = 3 # Keep first n1 elements
n2 = 3 # Keep last n2 elements

print(list(np.delete(x,(np.r_[n1:len(x)-n2])))) # [1 6 2 1 6 1]

edited Dec 08 '18 at 10:29

answered Dec 08 '18 at 06:59

b-fg

3,959
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Numpy answer on a native python question. Almost always overkill. – Andras Deak -- Слава Україні Dec 08 '18 at 07:00
It meets OP request: "Is there a way to just keep it same brackets? x[...,...] similar to this one? " I think under this specific request is not an overkill. – b-fg Dec 08 '18 at 07:03
Also the downvote is specified for non useful answers, which I do not think this is one. – b-fg Dec 08 '18 at 07:04
1

The result isn't even a list which OP wants. Importing numpy for a trivial list operation is overkill by definition. Same as importing pandas just to parse a simple csv. It's not a useful answer in my opinion. Just because OP wants a single pair of brackets is not reason enough to write poor code. – Andras Deak -- Слава Україні Dec 08 '18 at 07:07
Changed the object-type issue. How would you do it like OP requests then? – b-fg Dec 08 '18 at 07:10
Like [that](https://stackoverflow.com/questions/53680150/how-to-slice-list-left-and-right-except-middle-part#comment94217866_53680150), posted half an hour ago. – Andras Deak -- Слава Україні Dec 08 '18 at 07:11
Fair, but this is just another way. Also good to know both these numpy functions. I will keep the answer up anyway. – b-fg Dec 08 '18 at 07:12

score -1 · Answer 2 · answered Dec 08 '18 at 07:55

-1

You could do: x[0:3]+x[4:7] or x[:3]+x[-3:]. The second one gets the first 3 elements from the last and the first three elements from the right.

answered Dec 08 '18 at 07:55

Travis Bumgarner

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How to slice list left and right, except middle part?

2 Answers2