BUG: Make nullable booleans numeric

doc/source/whatsnew/v1.1.0.rst

@@ -846,6 +846,7 @@ ExtensionArray
 - Fixed bug that caused :meth:`Series.__repr__()` to crash for extension types whose elements are multidimensional arrays (:issue:`33770`).
 - Fixed bug where :meth:`Series.update` would raise a ``ValueError`` for ``ExtensionArray`` dtypes with missing values (:issue:`33980`)
 - Fixed bug where :meth:`StringArray.memory_usage` was not implemented (:issue:`33963`)
+- Fixed bug where :meth:`DataFrameGroupBy` would ignore the ``min_count`` argument for aggregations on nullable boolean dtypes (:issue:`34051`)
 - Fixed bug that `DataFrame(columns=.., dtype='string')` would fail (:issue:`27953`, :issue:`33623`)
 
 

pandas/core/arrays/boolean.py

@@ -93,6 +93,10 @@ def __repr__(self) -> str:
     def _is_boolean(self) -> bool:
         return True
 
+    @property
+    def _is_numeric(self) -> bool:
+        return True
+
     def __from_arrow__(
         self, array: Union["pyarrow.Array", "pyarrow.ChunkedArray"]
     ) -> "BooleanArray":

pandas/core/dtypes/cast.py

@@ -312,12 +312,14 @@ def maybe_cast_result_dtype(dtype: DtypeObj, how: str) -> DtypeObj:
     DtypeObj
         The desired dtype of the result.
     """
-    d = {
-        (np.dtype(np.bool), "add"): np.dtype(np.int64),
-        (np.dtype(np.bool), "cumsum"): np.dtype(np.int64),
-        (np.dtype(np.bool), "sum"): np.dtype(np.int64),
-    }
-    return d.get((dtype, how), dtype)
+    from pandas.core.arrays.boolean import BooleanDtype
+    from pandas.core.arrays.integer import Int64Dtype
+
+    if how in ["add", "cumsum", "sum"] and (dtype == np.dtype(np.bool)):
+        return np.dtype(np.int64)
+    elif how in ["add", "cumsum", "sum"] and isinstance(dtype, BooleanDtype):
+        return Int64Dtype()
+    return dtype
 
 
 def maybe_cast_to_extension_array(cls: Type["ExtensionArray"], obj, dtype=None):

pandas/core/groupby/ops.py

@@ -485,7 +485,7 @@ def _cython_operation(
             values = values.view("int64")
             is_numeric = True
         elif is_bool_dtype(values.dtype):
-            values = ensure_float64(values)
+            values = ensure_int_or_float(values)
         elif is_integer_dtype(values):
             # we use iNaT for the missing value on ints
             # so pre-convert to guard this condition

pandas/tests/extension/test_boolean.py

@@ -326,6 +326,23 @@ def test_in_numeric_groupby(self, data_for_grouping):
 
         tm.assert_index_equal(result, expected)
 
+    @pytest.mark.parametrize("min_count", [0, 10])
+    def test_groupby_sum_mincount(self, data_for_grouping, min_count):
+        df = pd.DataFrame({"A": [1, 1, 2, 2, 3, 3, 1], "B": data_for_grouping})
+        result = df.groupby("A").sum(min_count=min_count)
+        if min_count == 0:
+            expected = pd.DataFrame(
+                {"B": pd.array([3, 0, 0], dtype="Int64")},
+                index=pd.Index([1, 2, 3], name="A"),
+            )
+            tm.assert_frame_equal(result, expected)
+        else:
+            expected = pd.DataFrame(
+                {"B": pd.array([pd.NA] * 3, dtype="Int64")},
+                index=pd.Index([1, 2, 3], name="A"),
+            )
+            tm.assert_frame_equal(result, expected)
+
 
 class TestNumericReduce(base.BaseNumericReduceTests):
     def check_reduce(self, s, op_name, skipna):