[Numpy-discussion] bug: wrong itemsizes between NumPy strings and numarray

[Francesc Altet]

Hi,

The PyTables test suite has just discovered a subtle bug when doing
conversions between NumPy strings and numarray. In principle I'd say
that this is a problem with numarray, but as this problem raised when
updating numpy to the latest SVN version, I don't know what to think,
frankly.

The problem can be seen in:

In [1]: import numpy

In [2]: numpy.__version__
Out[2]: '0.9.7.2466'

In [3]: from numarray import strings

In [4]: strings.array(numpy.array(['aa'],'S1')).itemsize()
Out[4]: 1

In [5]: strings.array(numpy.array(['aa'],'S2')).itemsize()
Out[5]: 2

In [6]: strings.array(numpy.array(['aa'],'S3')).itemsize()
Out[6]: 2

In [7]: strings.array(numpy.array(['aa'],'S30')).itemsize()
Out[7]: 2

i.e. the numarray element size out of the conversion is always 2 (i.e.
the actual size of the element in the list), despite that the original
NumPy object can have bigger sizes.

However, with another NumPy version (dated from 3 weeks ago or so):

In [1]: import numpy

In [2]: numpy.__version__
Out[2]: '0.9.7.2278'

In [3]: from numarray import strings

In [4]: strings.array(numpy.array(['aa'],'S1')).itemsize()
Out[4]: 1

In [5]: strings.array(numpy.array(['aa'],'S2')).itemsize()
Out[5]: 2

In [6]: strings.array(numpy.array(['aa'],'S3')).itemsize()
Out[6]: 3

In [7]: strings.array(numpy.array(['aa'],'S30')).itemsize()
Out[7]: 30

i.e. it works as intended.

I report the bug here because I don't know who is the actual culprit.

Cheers,

-- 
>0,0<   Francesc Altet     http://www.carabos.com/
V   V   Cárabos Coop. V.   Enjoy Data
 "-"