Remove dtype as a required argument for StringScalar

Since StringDType doesn't take any parameters there's no
need to save the dtype along with the scalar instance. We
can always create a new StringDType instance on-the-fly.

Author: ngoldbaum

stringdtype/stringdtype/scalar.py

@@ -2,11 +2,6 @@
 
 
 class StringScalar(str):
-    def __new__(cls, value, dtype):
-        instance = super().__new__(cls, value)
-        instance.dtype = dtype
-        return instance
-
     def partition(self, sep):
         ret = super().partition(sep)
         return (str(ret[0]), str(ret[1]), str(ret[2]))

stringdtype/stringdtype/src/dtype.c

@@ -68,7 +68,7 @@ string_discover_descriptor_from_pyobject(PyArray_DTypeMeta *NPY_UNUSED(cls),
         return NULL;
     }
 
-    PyArray_Descr *ret = (PyArray_Descr *)PyObject_GetAttrString(obj, "dtype");
+    PyArray_Descr *ret = (PyArray_Descr *)new_stringdtype_instance();
     if (ret == NULL) {
         return NULL;
     }
@@ -143,7 +143,7 @@ stringdtype_getitem(StringDTypeObject *descr, char **dataptr)
     }
 
     PyObject *res = PyObject_CallFunctionObjArgs((PyObject *)StringScalar_Type,
-                                                 val_obj, descr, NULL);
+                                                 val_obj, NULL);
 
     if (res == NULL) {
         return NULL;

stringdtype/tests/test_stringdtype.py

@@ -14,7 +14,7 @@ def string_list():
 
 
 def test_scalar_creation():
-    assert str(StringScalar("abc", StringDType())) == "abc"
+    assert str(StringScalar("abc")) == "abc"
 
 
 def test_dtype_creation():
@@ -42,12 +42,11 @@ def test_array_creation_utf8(data):
 
 
 def test_array_creation_scalars(string_list):
-    dtype = StringDType()
     arr = np.array(
         [
-            StringScalar("abc", dtype=dtype),
-            StringScalar("def", dtype=dtype),
-            StringScalar("ghi", dtype=dtype),
+            StringScalar("abc"),
+            StringScalar("def"),
+            StringScalar("ghi"),
         ]
     )
     assert repr(arr) == repr(np.array(string_list, dtype=StringDType()))
@@ -98,7 +97,7 @@ def test_unicode_casts(string_list):
 def test_insert_scalar(string_list):
     dtype = StringDType()
     arr = np.array(string_list, dtype=dtype)
-    arr[1] = StringScalar("what", dtype=dtype)
+    arr[1] = StringScalar("what")
     assert repr(arr) == repr(np.array(["abc", "what", "ghi"], dtype=dtype))