[Pytables-users] Re: Tables with arbitrary number of columns

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

[I'm CC-ing this to pytables-users. Hope you don't mind]

A Wednesday 15 June 2005 11:09, v=E0reu escriure:
> Hi Francesc!
>
> I have contacted you before about using PyTables for storing simulation
> data. We have decided to make use of your program since it has so many
> powerful features. Nevertheless I have a question regarding the creation =
of
> tables. Suppose we have a class like this (taken from your example):
>
> class Particle(IsDescription):
>     name      =3D StringCol(16)   # 16-character String
>     idnumber  =3D Int64Col()      # Signed 64-bit integer
>     ADCcount  =3D UInt16Col()     # Unsigned short integer
>     TDCcount  =3D UInt8Col()      # unsigned byte
>     grid_i    =3D Int32Col()      # integer
>     grid_j    =3D IntCol()        # integer (equivalent to Int32Col)
>     pressure  =3D Float32Col()    # float  (single-precision)
>     energy    =3D FloatCol()      # double (double-precision)
>
> and later on we create a table with:
>
> table =3D h5file.createTable(group, 'readout', Particle, "Readout example=
")
>
> The third parameter of the createTable function is the name of the class,
> in this example Particle - a user record for characterizing 8 attributes
> (name, idnumber, ADCcount …), which correspond to 8 columns of a
> table. Now, suppose I want to write a new function for dealing with tables
> where a user can specify an arbitrary number of columns with different da=
ta
> types. How can I make a custom class (Particle in this example) to change
> its number of attributes corresponding to user request/input of the number
> of columns that it wishes to have?
> I hope I was clear enough.

I am not sure to completely understand you, but perhaps creating a
table using a dictionary as a description would be enough for you?

Look at:

http://pytables.sourceforge.net/html-doc/x912.html#secondExample

for an example of using dictionaries as table descriptors.

HTH,

=2D-=20
>0,0<   Francesc Altet =A0 =A0 http://www.carabos.com/
V   V   C=E1rabos Coop. V. =A0=A0Enjoy Data
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