difference in behavior when writing unicode string to attrs (setter vs .create API)

[PiRK]

Hi.
I'm aware that there are many issues already open about writing lists of unicode strings to h5py attributes. But I found that the same problem exists when I try to write a single unicode string using the .create API, while it works fine when I write the string using the setter API.

This works:
h5f["toto"].attrs["toto"] = u"toto"

This causes an error:
h5f["toto"].attrs.create("toto", data=u"toto")
TypeError: No conversion path for dtype: dtype('<U4')

Is there a reason for this difference in behavior? Or would it be possible to also add the if dtype is None: dtype = base.guess_dtype(value) line to the create method, like it is done in __setitem__ ? (https://github.com/h5py/h5py/blob/master/h5py/_hl/attrs.py#L102)

Summary of the h5py configuration

h5py 2.8.0
HDF5 1.10.2
Python 2.7.9 (default, Jun 29 2016, 13:08:31)
[GCC 4.9.2]
sys.platform linux2
sys.maxsize 9223372036854775807
numpy 1.14.5

[aragilar]

This does seem odd. We should look where guess_dtype is used currently, and try to reduce duplication of conversion code.