Bug in Series constructor returning wrong missing values (#43026)

Author: phofl

doc/source/whatsnew/v1.4.0.rst

@@ -266,6 +266,7 @@ Numeric
 Conversion
 ^^^^^^^^^^
 - Bug in :class:`UInt64Index` constructor when passing a list containing both positive integers small enough to cast to int64 and integers too large too hold in int64 (:issue:`42201`)
+- Bug in :class:`Series` constructor returning 0 for missing values with dtype ``int64`` and ``False`` for dtype ``bool`` (:issue:`43017`, :issue:`43018`)
 -
 
 Strings

pandas/core/series.py

@@ -475,7 +475,7 @@ def _init_dict(self, data, index=None, dtype: Dtype | None = None):
         elif index is not None:
             # fastpath for Series(data=None). Just use broadcasting a scalar
             # instead of reindexing.
-            values = na_value_for_dtype(pandas_dtype(dtype))
+            values = na_value_for_dtype(pandas_dtype(dtype), compat=False)
             keys = index
         else:
             keys, values = (), []

pandas/tests/series/methods/test_astype.py

@@ -356,6 +356,13 @@ def test_astype_bytes(self):
         result = Series(["foo", "bar", "baz"]).astype(bytes)
         assert result.dtypes == np.dtype("S3")
 
+    def test_astype_nan_to_bool(self):
+        # GH#43018
+        ser = Series(np.nan, dtype="object")
+        result = ser.astype("bool")
+        expected = Series(True, dtype="bool")
+        tm.assert_series_equal(result, expected)
+
 
 class TestAstypeString:
     @pytest.mark.parametrize(

pandas/tests/series/test_constructors.py

@@ -1776,6 +1776,18 @@ def test_constructor_with_pandas_dtype(self):
         ser2 = Series(vals, dtype=dtype)
         tm.assert_series_equal(ser, ser2)
 
+    def test_constructor_int_dtype_missing_values(self):
+        # GH#43017
+        result = Series(index=[0], dtype="int64")
+        expected = Series(np.nan, index=[0], dtype="float64")
+        tm.assert_series_equal(result, expected)
+
+    def test_constructor_bool_dtype_missing_values(self):
+        # GH#43018
+        result = Series(index=[0], dtype="bool")
+        expected = Series(True, index=[0], dtype="bool")
+        tm.assert_series_equal(result, expected)
+
 
 class TestSeriesConstructorIndexCoercion:
     def test_series_constructor_datetimelike_index_coercion(self):