BUG: Fix downcast argument for DataFrame.fillna()

closes pandas-dev#15277

Author: Albert Villanova del Moral <[email protected]>

Author: Albert Villanova del Moral

pandas/core/generic.py

@@ -3347,7 +3347,7 @@ def fillna(self, value=None, method=None, axis=None, inplace=False,
                     if k not in result:
                         continue
                     obj = result[k]
-                    obj.fillna(v, limit=limit, inplace=True)
+                    obj.fillna(v, limit=limit, inplace=True, downcast=downcast)
                 return result
             elif not is_list_like(value):
                 new_data = self._data.fillna(value=value, limit=limit,

pandas/tests/frame/test_missing.py

@@ -252,6 +252,19 @@ def test_fillna(self):
         result = df.fillna(value={'Date': df['Date2']})
         assert_frame_equal(result, expected)
 
+    def test_fillna_downcast(self):
+	# infer int64 from float64
+	df = pd.DataFrame({'a': [1., np.nan]})
+	result = df.fillna(0, downcast='infer')
+	expected = pd.DataFrame({'a': [1, 0]})
+	assert_frame_equal(result, expected)
+
+	# infer int64 from float64 when fillna value is a dict
+	df = pd.DataFrame({'a': [1., np.nan]})
+	result = df.fillna({'a': 0}, downcast='infer')
+	expected = pd.DataFrame({'a': [1, 0]})
+	assert_frame_equal(result, expected)
+
     def test_fillna_dtype_conversion(self):
         # make sure that fillna on an empty frame works
         df = DataFrame(index=["A", "B", "C"], columns=[1, 2, 3, 4, 5])

pandas/tests/series/test_missing.py

@@ -268,6 +268,19 @@ def test_datetime64tz_fillna_round_issue(self):
 
         assert_series_equal(filled, expected)
 
+    def test_fillna_downcast(self):
+        # infer int64 from float64
+	s = pd.Series([1., np.nan])
+	result = s.fillna(0, downcast='infer')
+	expected = pd.Series([1, 0])
+	assert_series_equal(result, expected)
+
+        # infer int64 from float64 when fillna value is a dict
+        s = pd.Series([1., np.nan])
+        result = s.fillna({1: 0}, downcast='infer')
+        expected = pd.Series([1, 0])
+        assert_series_equal(result, expected)
+
     def test_fillna_int(self):
         s = Series(np.random.randint(-100, 100, 50))
         s.fillna(method='ffill', inplace=True)