BUG: fix .loc.__setitem__ not raising when using too many indexers

Author: DriesSchaumont

pandas/core/indexing.py

@@ -911,7 +911,7 @@ def _getitem_nested_tuple(self, tup: tuple):
                 #  we are only getting non-hashable tuples, in particular ones
                 #  that themselves contain a slice entry
                 # See test_loc_series_getitem_too_many_dimensions
-                raise ValueError("Too many indices")
+                raise IndexingError("Too many indexers")
 
             # this is a series with a multi-index specified a tuple of
             # selectors
@@ -1231,6 +1231,11 @@ def _convert_to_indexer(self, key, axis: int):
         is_int_index = labels.is_integer()
         is_int_positional = is_integer(key) and not is_int_index
 
+        if isinstance(key, tuple) and not isinstance(labels, MultiIndex):
+            if len(key) > 1:
+                raise IndexingError("Too many indexers")
+            key = key[0]
+
         if is_scalar(key) or (isinstance(labels, MultiIndex) and is_hashable(key)):
             # Otherwise get_loc will raise InvalidIndexError
 
@@ -1262,7 +1267,7 @@ def _convert_to_indexer(self, key, axis: int):
         if is_nested_tuple(key, labels):
             if self.ndim == 1 and any(isinstance(k, tuple) for k in key):
                 # GH#35349 Raise if tuple in tuple for series
-                raise ValueError("Too many indices")
+                raise IndexingError("Too many indexers")
             return labels.get_locs(key)
 
         elif is_list_like_indexer(key):

pandas/tests/indexing/test_iloc.py

@@ -1189,6 +1189,16 @@ def test_iloc_getitem_setitem_fancy_exceptions(self, float_frame):
             # GH#32257 we let numpy do validation, get their exception
             float_frame.iloc[:, :, :] = 1
 
+    def test_iloc_setitem_indexer_length(self):
+        # GH#13831
+        ser = Series([10])
+        msg = "too many indices for array: array is 1-dimensional, but 2 were indexed"
+        with pytest.raises(IndexError, match=msg):
+            ser.iloc[0, 0] = 1000
+
+        with pytest.raises(IndexingError, match="Too many indexers"):
+            ser.iloc[0, 0]
+
     # TODO(ArrayManager) "split" path doesn't properly implement DataFrame indexer
     @td.skip_array_manager_not_yet_implemented
     def test_iloc_frame_indexer(self):

pandas/tests/indexing/test_loc.py

@@ -2715,6 +2715,17 @@ def test_loc_getitem_multiindex_tuple_level():
     assert result2 == 6
 
 
+def test_loc_setitem_indexer_length():
+    # GH#13831
+    ser = Series([10])
+    msg = "Too many indexers"
+    with pytest.raises(IndexingError, match=msg):
+        ser.loc[0, 0] = 1000
+
+    with pytest.raises(IndexingError, match=msg):
+        ser.loc[0, 0]
+
+
 class TestLocSeries:
     @pytest.mark.parametrize("val,expected", [(2 ** 63 - 1, 3), (2 ** 63, 4)])
     def test_loc_uint64(self, val, expected):
@@ -2889,11 +2900,11 @@ def test_loc_series_getitem_too_many_dimensions(self, indexer):
             index=MultiIndex.from_tuples([("A", "0"), ("A", "1"), ("B", "0")]),
             data=[21, 22, 23],
         )
-        msg = "Too many indices"
-        with pytest.raises(ValueError, match=msg):
+        msg = "Too many indexers"
+        with pytest.raises(IndexingError, match=msg):
             ser.loc[indexer, :]
 
-        with pytest.raises(ValueError, match=msg):
+        with pytest.raises(IndexingError, match=msg):
             ser.loc[indexer, :] = 1
 
     def test_loc_setitem(self, string_series):