TST: Add C-side "Scaled float" example

This adds a C-side scaled float (actually double), that is available
as:

     SF = np.core._multiarray_umath._get_sfloat_dtype()

It supports different scaling factors:

    a = np.arange(10.).astype(SF(2.))
    b = np.arange(10.).astype(SF(0.5))

and casting from double (used there).

This commit makes tiny changes in NumPy to support correct printing.

1 files changed, 6 insertions, 1 deletions

diff --git a/numpy/core/arrayprint.py b/numpy/core/arrayprint.py
index f16bcfd39..2a4bef669 100644
--- a/numpy/core/arrayprint.py
+++ b/numpy/core/arrayprint.py
@@ -420,7 +420,9 @@ def _get_format_function(data, **options):
     dtype_ = data.dtype
     dtypeobj = dtype_.type
     formatdict = _get_formatdict(data, **options)
-    if issubclass(dtypeobj, _nt.bool_):
+    if dtypeobj is None:
+        return formatdict["numpystr"]()
+    elif issubclass(dtypeobj, _nt.bool_):
         return formatdict['bool']()
     elif issubclass(dtypeobj, _nt.integer):
         if issubclass(dtypeobj, _nt.timedelta64):
@@ -1408,6 +1410,9 @@ def dtype_short_repr(dtype):
     >>> dt = np.int64([1, 2]).dtype
     >>> assert eval(dtype_short_repr(dt)) == dt
     """
+    if type(dtype).__repr__ != np.dtype.__repr__:
+        # TODO: Custom repr for user DTypes, logic should likely move.
+        return repr(dtype)
     if dtype.names is not None:
         # structured dtypes give a list or tuple repr
         return str(dtype)