stringdtype: problem displaying a structured array containing a StringDType

[WarrenWeckesser]

I ran into this exception when I tried to use a StringDType in a structured array:

In [47]: dt = np.dtype([('id', int), ('value', float), ('key', StringDType())])

In [48]: dt
Out[48]: ---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
File ~/py3.11.5/lib/python3.11/site-packages/IPython/core/formatters.py:708, in PlainTextFormatter.__call__(self, obj)
    701 stream = StringIO()
    702 printer = pretty.RepresentationPrinter(stream, self.verbose,
    703     self.max_width, self.newline,
    704     max_seq_length=self.max_seq_length,
    705     singleton_pprinters=self.singleton_printers,
    706     type_pprinters=self.type_printers,
    707     deferred_pprinters=self.deferred_printers)
--> 708 printer.pretty(obj)
    709 printer.flush()
    710 return stream.getvalue()

File ~/py3.11.5/lib/python3.11/site-packages/IPython/lib/pretty.py:410, in RepresentationPrinter.pretty(self, obj)
    407                         return meth(obj, self, cycle)
    408                 if cls is not object \
    409                         and callable(cls.__dict__.get('__repr__')):
--> 410                     return _repr_pprint(obj, self, cycle)
    412     return _default_pprint(obj, self, cycle)
    413 finally:

File ~/py3.11.5/lib/python3.11/site-packages/IPython/lib/pretty.py:778, in _repr_pprint(obj, p, cycle)
    776 """A pprint that just redirects to the normal repr function."""
    777 # Find newlines and replace them with p.break_()
--> 778 output = repr(obj)
    779 lines = output.splitlines()
    780 with p.group():

File ~/py3.11.5/lib/python3.11/site-packages/numpy/core/_dtype.py:46, in __repr__(dtype)
     45 def __repr__(dtype):
---> 46     arg_str = _construction_repr(dtype, include_align=False)
     47     if dtype.isalignedstruct:
     48         arg_str = arg_str + ", align=True"

File ~/py3.11.5/lib/python3.11/site-packages/numpy/core/_dtype.py:96, in _construction_repr(dtype, include_align, short)
     69 """
     70 Creates a string repr of the dtype, excluding the 'dtype()' part
     71 surrounding the object. This object may be a string, a list, or
   (...)
     93     provided as the second parameter.
     94 """
     95 if dtype.fields is not None:
---> 96     return _struct_str(dtype, include_align=include_align)
     97 elif dtype.subdtype:
     98     return _subarray_str(dtype)

File ~/py3.11.5/lib/python3.11/site-packages/numpy/core/_dtype.py:310, in _struct_str(dtype, include_align)
    305 def _struct_str(dtype, include_align):
    306     # The list str representation can't include the 'align=' flag,
    307     # so if it is requested and the struct has the aligned flag set,
    308     # we must use the dict str instead.
    309     if not (include_align and dtype.isalignedstruct) and _is_packed(dtype):
--> 310         sub = _struct_list_str(dtype)
    312     else:
    313         sub = _struct_dict_str(dtype, include_align)

File ~/py3.11.5/lib/python3.11/site-packages/numpy/core/_dtype.py:297, in _struct_list_str(dtype)
    292     item += "{}, {}".format(
    293         _construction_repr(base, short=True),
    294         shape
    295     )
    296 else:
--> 297     item += _construction_repr(fld_dtype, short=True)
    299 item += ")"
    300 items.append(item)

File ~/py3.11.5/lib/python3.11/site-packages/numpy/core/_dtype.py:100, in _construction_repr(dtype, include_align, short)
     98     return _subarray_str(dtype)
     99 else:
--> 100     return _scalar_str(dtype, short=short)

File ~/py3.11.5/lib/python3.11/site-packages/numpy/core/_dtype.py:156, in _scalar_str(dtype, short)
    153     return dtype.type.__name__
    155 else:
--> 156     raise RuntimeError(
    157         "Internal error: NumPy dtype unrecognized type number")

RuntimeError: Internal error: NumPy dtype unrecognized type number

[ngoldbaum]

Probably needs an upstream numpy issue, you'd hit the same error with any user-defined dtype using the new dtype API.

[ngoldbaum]

I opened numpy/numpy#24758