Hello List, I'm working on an extension for pytables, a package to store numpy arrays into hdf5 files. hdf5 supports the additional datatype "reference", which makes sense only in an hdf5 context. In order to be able to use them in pytables, I figured the best idea is to define a user-defined datatype, register it with PyArray_RegisterDataType and insert it into the typeDict. This all works fine, except that spurious exceptions are risen after one has called dtype("r") (I use r as the type code). I tracked it down to the function PyArray_DescrConverter, which calls PyArray_DescrFromType (just after the finish: label). This function sets a python exception with PyErr_SetString and returns NULL. But the calling function ignores this, and returns successfully. The exception then is still dangling, and at a later time will be risen in completely unrelated code. I guess a PyErr_Clear should be added at the beginning of the if-clause to solve the problem. I submitted this bug as Ticket #1255 to the numpy trac system, where you can also find the code that triggered the bug. Greetings Martin Teichmann