[Numpy-discussion] List with numpy semantics

josef.pktd@gmai... josef.pktd@gmai...
Tue Nov 2 21:21:37 CDT 2010

On Tue, Nov 2, 2010 at 10:02 PM, Nikolaus Rath <Nikolaus@rath.org> wrote:
> Gerrit Holl <gerrit.holl@gmail.com> writes:
>> On 31 October 2010 17:10, Nikolaus Rath <Nikolaus@rath.org> wrote:
>>> Hello,
>>> I have a couple of numpy arrays which belong together. Unfortunately
>>> they have different dimensions, so I can't bundle them into a higher
>>> dimensional array.
>>> My solution was to put them into a Python list instead. But
>>> unfortunately this makes it impossible to use any ufuncs.
>>> Has someone else encountered a similar problem and found a nice
>>> solution? Something like a numpy list maybe?
>> You could try a record array with a clever dtype, maybe?
> It seems that this requires more cleverness than I have... Could you
> give me an example? How do I replace l in the following code with a
> record array?
> l = list()
> l.append(np.arange(3))
> l.append(np.arange(42))
> l.append(np.arange(9))
> for i in range(len(l)):
>   l[i] += 32

Depending on how you want to use it, it might be more convenient to
use masked arrays or fill with nan (like pandas and larry) to get a
rectangular array. it might be more convenient for some things, but if
the sizes differ a lot then it might not be more efficient.


> Thanks,
>   -Nikolaus
> --
>  »Time flies like an arrow, fruit flies like a Banana.«
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