[Nexus] 2D character arrays in python binding?

[Paul Kienzle]

On Jan 29, 2009, at 10:44 AM, Akeroyd, FA (Freddie) wrote:

> Carlos,
>
> The 4.2 release candidate of the NeXus API supports two dimensional
> character arrays for HDF4 and HDF5 - XML might suffer problems if  
> there
> are embedded newlines etc. The API is expecting a square array of
> characters i.e. it will not pad short strings with spaces. I got the
> python API to work by using:
>
> {{{
> filenames=['bar1      ','longerbar2','bar3      ']
> ...
> f.makedata('filenames','char',[3,10])
> f.opendata('filenames')
> f.putdata(''.join(filenames))
> ...
> }}}
>
> However it should be possible for us to get the python API to spot a
> string list and do the necessary space padding and joining for you
> automatically.

The natural numpy translation of the above example is as a length 3  
array of type '|S10', not a 3x10 array of '|S1'.  If you do  
ascontiguousarray(['a','perfect','day'],'|S10') for example, then it  
will record the correct information.  This should scale to  
multidimensional string arrays if they are needed.

The pad character in this case will be '\0' rather than ' '.  Is this  
going to be a problem for the HDF backend?

- Paul