how to improve this cycle (extracting data from structured array)?
Tim Chase
python.list at tim.thechases.com
Thu Feb 11 13:08:31 CET 2010
Alexzive wrote:
> I am just wondering if there is a quick way to improve this algorithm
> [N is a structured array which hold info about the nodes n of a finite
> element mesh, and n is about 300.000). I need to extract info from N
> and put it in to a 3*n matrix NN which I reshape then with numpy. I
> think to "append" is quite unefficient:
>
> ***********************************************************
> N = odb.rootAssembly.instances['PART-1-1'].nodes
>
> NN=[]
>
> B=[0,0,0]
> #auxsiliar vector
> for i in range(len(N)):
> B[0] = N[i].label
> B[1] = N[i].coordinates[0]
> B[2] = N[i].coordinates[1]
> NN = append(NN,B)
Usually this would be written with a list-comprehension,
something like
nn = [(x.label, x.coordinates[0], x.coordinates[1])
for x in N]
or if you really need lists-of-lists instead of lists-of-tuples:
nn = [[x.label, x.coordinates[0], x.coordinates[1]]
for x in N]
-tkc
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