Added test and documentation for qcut Float64DType support

Author: taytzehao

doc/source/whatsnew/v1.3.0.rst

@@ -663,7 +663,7 @@ Conversion
 - Bug in :class:`Index` construction silently ignoring a passed ``dtype`` when the data cannot be cast to that dtype (:issue:`21311`)
 - Bug in :meth:`StringArray.astype` falling back to numpy and raising when converting to ``dtype='categorical'`` (:issue:`40450`)
 - Bug in :class:`DataFrame` construction with a dictionary containing an arraylike with ``ExtensionDtype`` and ``copy=True`` failing to make a copy (:issue:`38939`)
--
+- Bug in :func:`_coerce_to_type` failing to convert ``Float64DType`` input into numpy array (:issue:`40730`)
 
 Strings
 ^^^^^^^

pandas/tests/reshape/test_qcut.py

@@ -301,3 +301,19 @@ def test_qcut_nullable_integer(q, any_nullable_int_dtype):
  expected = qcut(arr.astype(float), q)
 
  tm.assert_categorical_equal(result, expected)
+ 
+
+@pytest.mark.parametrize("Data_type,Data_type_string",
+ [
+ (pd.Float64Dtype(),"Float64Dtype"),
+ (pd.Int64Dtype(),"Int64Dtype")
+ ]
+ )
+def test_qcut_numeric_dtype(Data_type,Data_type_string):
+ series = pd.Series([1.0, 2.0, 3.0, 4.0], dtype=Data_type)
+
+ try:
+ pd.qcut(series,2)
+ except:
+ Fail_string=Data_type_string+" is not supported"
+ pytest.fail(msg=Fail_string )