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Groups > comp.lang.python > #37855 > unrolled thread
| Started by | "C. Ng" <ngcbmy@gmail.com> |
|---|---|
| First post | 2013-01-29 00:41 -0800 |
| Last post | 2013-01-29 15:05 -0500 |
| Articles | 5 — 5 participants |
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numpy array operation "C. Ng" <ngcbmy@gmail.com> - 2013-01-29 00:41 -0800
Re: numpy array operation Peter Otten <__peter__@web.de> - 2013-01-29 10:28 +0100
Re: numpy array operation Tim Williams <tjandacw@cox.net> - 2013-01-29 04:59 -0800
Re: numpy array operation Alok Singhal <as8ca@virginia.edu> - 2013-01-29 18:49 +0000
Re: numpy array operation Terry Reedy <tjreedy@udel.edu> - 2013-01-29 15:05 -0500
| From | "C. Ng" <ngcbmy@gmail.com> |
|---|---|
| Date | 2013-01-29 00:41 -0800 |
| Subject | numpy array operation |
| Message-ID | <f94d7654-2b87-404b-a0b0-76f1ccf8ee6c@googlegroups.com> |
Is there a numpy operation that does the following to the array? 1 2 ==> 4 3 3 4 2 1 Thanks in advance.
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| From | Peter Otten <__peter__@web.de> |
|---|---|
| Date | 2013-01-29 10:28 +0100 |
| Message-ID | <mailman.1167.1359451658.2939.python-list@python.org> |
| In reply to | #37855 |
C. Ng wrote:
> Is there a numpy operation that does the following to the array?
>
> 1 2 ==> 4 3
> 3 4 2 1
How about
>>> a
array([[1, 2],
[3, 4]])
>>> a[::-1].transpose()[::-1].transpose()
array([[4, 3],
[2, 1]])
Or did you mean
>>> a.reshape((4,))[::-1].reshape((2,2))
array([[4, 3],
[2, 1]])
Or even
>>> -a + 5
array([[4, 3],
[2, 1]])
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| From | Tim Williams <tjandacw@cox.net> |
|---|---|
| Date | 2013-01-29 04:59 -0800 |
| Message-ID | <3111692c-2341-4c6d-9bea-35d6167a0c94@googlegroups.com> |
| In reply to | #37855 |
On Tuesday, January 29, 2013 3:41:54 AM UTC-5, C. Ng wrote:
> Is there a numpy operation that does the following to the array?
>
>
>
> 1 2 ==> 4 3
>
> 3 4 2 1
>
>
>
> Thanks in advance.
>>> import numpy as np
>>> a=np.array([[1,2],[3,4]])
>>> a
array([[1, 2],
[3, 4]])
>>> np.fliplr(np.flipud(a))
array([[4, 3],
[2, 1]])
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| From | Alok Singhal <as8ca@virginia.edu> |
|---|---|
| Date | 2013-01-29 18:49 +0000 |
| Message-ID | <ke95jk$v42$1@dont-email.me> |
| In reply to | #37855 |
On Tue, 29 Jan 2013 00:41:54 -0800, C. Ng wrote:
> Is there a numpy operation that does the following to the array?
>
> 1 2 ==> 4 3
> 3 4 2 1
>
> Thanks in advance.
How about:
>>> import numpy as np
>>> a = np.array([[1,2],[3,4]])
>>> a
array([[1, 2],
[3, 4]])
>>> a[::-1, ::-1]
array([[4, 3],
[2, 1]])
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| From | Terry Reedy <tjreedy@udel.edu> |
|---|---|
| Date | 2013-01-29 15:05 -0500 |
| Message-ID | <mailman.1192.1359489934.2939.python-list@python.org> |
| In reply to | #37895 |
On 1/29/2013 1:49 PM, Alok Singhal wrote: > On Tue, 29 Jan 2013 00:41:54 -0800, C. Ng wrote: > >> Is there a numpy operation that does the following to the array? >> >> 1 2 ==> 4 3 >> 3 4 2 1 >> >> Thanks in advance. > > How about: > >>>> import numpy as np >>>> a = np.array([[1,2],[3,4]]) >>>> a > array([[1, 2], [3, 4]]) >>>> a[::-1, ::-1] > array([[4, 3], [2, 1]]) > Nice. The regular Python equivalent is a = [[1,2],[3,4]] print([row[::-1] for row in a[::-1]]) >>> [[4, 3], [2, 1]] The second slice can be replaced with reversed(a), which returns an iterator, to get [row[::-1] for row in reversed(a)] The first slice would have to be list(reversed(a)) to get the same result. -- Terry Jan Reedy
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