Re: [Pytables-users] ValueError when a list of numarray.arrays used.

[Francesc A. <fa...@py...>]

A Diumenge 10 Octubre 2004 05:59, Shin, Daehyok va escriure:
> Assuming at every simulation step I got a numeric array of 100 rows and 10
> cols,
> what is the most efficient way to append it to Table?

You can do something like:

from numarray import *
from tables import *

class Cols(IsDescription):
    V1 = FloatCol(shape=10)

f = openFile("test.hd5", "w")
tab = f.createTable("/","Data",Cols,"Data")

for i in range(10):
    # d simulates the output of your simulation step
    d = arange(i, 1000+i, shape=(100,10), type=Float64)
    tab.append([d])
    
f.close()

i.e. declaring a column with dimension 10.

> I want  to use Table rather than EArray because of explicit column names.

In that case, you can't use the recipe above. I would suggest you getting a
numarray.records.RecArray object from every step of your simulation code.
Then, you can feed the RecArray to Table.append() without any problem.

By the way, after thinking a bit about passing lists of numarray/Numeric to
the Table.append() method, I came to the conclusion that this is possible,
although this use is meant for multidimensional columns. For example:

from numarray import *
from tables import *

class Cols(IsDescription):
    V1 = FloatCol(shape=10)
    V2 = IntCol(shape=5)

f = openFile("test2.hd5", "w")
tab = f.createTable("/","Data",Cols,"Data")

for i in range(10):
    # d simulates the output of your simulation step
    d = arange(i, 1000+i, shape=(100,10), type=Float64)
    e = arange(i, 500+i, shape=(100,5), type=Int32)
    tab.append([d, e])
    
f.close()

works without problems. Maybe I should specify in the docs that you can use
lists of Numeric/numarray objects *only* in case of multimensional columns.

Cheers,

-- 
Francesc Alted