[Numpy-discussion] convert dictionary of arrays into single array

John Salvatier jsalvati at u.washington.edu
Wed Mar 16 10:38:27 EDT 2011

I think he wants to stack them (same widths) so stacking them should be

On Wed, Mar 16, 2011 at 7:30 AM, Bruce Southey <bsouthey at gmail.com> wrote:

>  On 03/16/2011 08:56 AM, John Salvatier wrote:
> Loop through to build a list of arrays, then use vstack on the list.
> On Wed, Mar 16, 2011 at 1:36 AM, John <washakie at gmail.com> wrote:
>> Hello,
>> I have a dictionary with structured arrays, keyed by integers 0...n.
>> There are no other keys in the dictionary.
>> What is the most efficient way to convert the dictionary of arrays to
>> a single array?
>> All the arrays have the same 'headings' and width, but different lengths.
>> Is there something I can do that would be more efficient than looping
>> through and using np.concatenate (vstack)?
>> --john
>> _______________________________________________
> Numpy does not permit a 'single' array of different shapes - ie a 'ragged
> array'.
> Sure you could convert this into a structured array (you know n so you can
> create an appropriate empty structured array and assign the array by looping
> across the dict) but that is still not a 'single' array. You can use a
> masked array where you masked the missing elements across your arrays.
> Francesc Alted pointed out in the 'ragged array implimentation' thread (
> http://mail.scipy.org/pipermail/numpy-discussion/2011-March/055219.html)
> that pytables does support this.
> Bruce
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