Fixed issues from review

Added whatsnew to 0.24
Added issue to tests comments
Moved some test
Added a test from the issue

Author: mariuspot

doc/source/whatsnew/v0.24.0.txt

@@ -656,6 +656,7 @@ Indexing
 - Fixed ``DataFrame[np.nan]`` when columns are non-unique (:issue:`21428`)
 - Bug when indexing :class:`DatetimeIndex` with nanosecond resolution dates and timezones (:issue:`11679`)
 - Bug where indexing with a Numpy array containing negative values would mutate the indexer (:issue:`21867`)
+- Bug where mixed indexes wouldn't allow integers for ``.at`` (:issue:`19860`)
 
 Missing
 ^^^^^^^

pandas/tests/indexing/test_indexing.py

@@ -610,6 +610,22 @@ def test_index_contains(self, index, val):
     def test_index_not_contains(self, index, val):
         assert val not in index
 
+    @pytest.mark.parametrize("index,val", [
+        (Index([0, 1, '2']), 0),
+        (Index([0, 1, '2']), '2'),
+    ])
+    def test_mixed_index_contains(self, index, val):
+        # GH 19860
+        assert val in index
+
+    @pytest.mark.parametrize("index,val", [
+        (Index([0, 1, '2']), '1'),
+        (Index([0, 1, '2']), 2),
+    ])
+    def test_mixed_index_not_contains(self, index, val):
+        # GH 19860
+        assert val not in index
+
     def test_index_type_coercion(self):
 
         with catch_warnings(record=True):
@@ -666,20 +682,6 @@ def test_index_type_coercion(self):
                     idxr(s2)['0'] = 0
                     assert s2.index.is_object()
 
-    @pytest.mark.parametrize("index,val", [
-        (Index([0, 1, '2']), '1'),
-        (Index([0, 1, '2']), 2),
-    ])
-    def test_mixed_index_not_contains(self, index, val):
-        assert val not in index
-
-    @pytest.mark.parametrize("index,val", [
-        (Index([0, 1, '2']), 0),
-        (Index([0, 1, '2']), '2'),
-    ])
-    def test_mixed_index_contains(self, index, val):
-        assert val in index
-
 
 class TestMisc(Base):
 
@@ -724,21 +726,16 @@ def test_float_index_at_iat(self):
         for i in range(len(s)):
             assert s.iat[i] == i + 1
 
-    def test_mixed_index_at_iat(self):
-        s = Series([1, 2, 3, 4, 5], index=['a', 'b', 'c', 1, 2])
-        for el, item in s.iteritems():
-            assert s.at[el] == item
-        for i in range(len(s)):
-            assert s.iat[i] == i + 1
-
     def test_mixed_index_assignment(self):
+        # GH 19860
         s = Series([1, 2, 3, 4, 5], index=['a', 'b', 'c', 1, 2])
         s.at['a'] = 11
         assert s.iat[0] == 11
         s.at[1] = 22
         assert s.iat[3] == 22
 
     def test_mixed_index_no_fallback(self):
+        # GH 19860
         s = Series([1, 2, 3, 4, 5], index=['a', 'b', 'c', 1, 2])
         with pytest.raises(KeyError):
             s.at[0]

pandas/tests/indexing/test_scalar.py

@@ -170,3 +170,36 @@ def test_at_with_tz(self):
 
         result = df.at[0, 'date']
         assert result == expected
+
+    def test_mixed_index_at_iat_loc_iloc_series(self):
+        # GH 19860
+        s = Series([1, 2, 3, 4, 5], index=['a', 'b', 'c', 1, 2])
+        for el, item in s.iteritems():
+            assert s.at[el] == s.loc[el] == item
+        for i in range(len(s)):
+            assert s.iat[i] == s.iloc[i] == i + 1
+
+        with pytest.raises(KeyError):
+            s.at[4]
+        with pytest.raises(KeyError):
+            s.loc[4]
+
+
+    def test_mixed_index_at_iat_loc_iloc_dataframe(self):
+        # GH 19860
+        df = DataFrame([[0, 1, 2, 3, 4], [5, 6, 7, 8, 9]],
+                          columns=['a', 'b', 'c', 1, 2])
+        for rowIdx, row in df.iterrows():
+            for el, item in row.iteritems():
+                assert df.at[rowIdx, el] == df.loc[rowIdx, el] == item
+
+        for row in range(2):
+            for i in range(5):
+                assert df.iat[row, i] == df.iloc[row, i] == row * 5 + i
+
+        with pytest.raises(KeyError):
+            df.at[0, 3]
+        with pytest.raises(KeyError):
+            df.loc[0, 3]
+
+