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

doc/source/whatsnew/v1.5.0.rst

@@ -264,6 +264,7 @@ Indexing
 - Bug in :meth:`DataFrame.iloc` where indexing a single row on a :class:`DataFrame` with a single ExtensionDtype column gave a copy instead of a view on the underlying data (:issue:`45241`)
 - Bug in setting a NA value (``None`` or ``np.nan``) into a :class:`Series` with int-based :class:`IntervalDtype` incorrectly casting to object dtype instead of a float-based :class:`IntervalDtype` (:issue:`45568`)
 - Bug in :meth:`Series.__setitem__` with a non-integer :class:`Index` when using an integer key to set a value that cannot be set inplace where a ``ValueError`` was raised insead of casting to a common dtype (:issue:`45070`)
+- Bug in :meth:`Series.loc.__setitem__` and :meth:`Series.loc.__getitem__` not raising when using multiple keys without using a :class:`MultiIndex` (:issue:`13831`)
 - Bug when setting a value too large for a :class:`Series` dtype failing to coerce to a common type (:issue:`26049`, :issue:`32878`)
 - Bug in :meth:`loc.__setitem__` treating ``range`` keys as positional instead of label-based (:issue:`45479`)
 - Bug in :meth:`Series.__setitem__` when setting ``boolean`` dtype values containing ``NA`` incorrectly raising instead of casting to ``boolean`` dtype (:issue:`45462`)

pandas/conftest.py

@@ -1734,6 +1734,14 @@ def indexer_sli(request):
     return request.param
 
 
+@pytest.fixture(params=[tm.loc, tm.iloc])
+def indexer_li(request):
+    """
+    Parametrize over loc.__getitem__, iloc.__getitem__
+    """
+    return request.param
+
+
 @pytest.fixture(params=[tm.setitem, tm.iloc])
 def indexer_si(request):
     """

pandas/core/indexing.py

@@ -934,7 +934,7 @@ 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
@@ -1260,6 +1260,14 @@ 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)
+            and self.ndim < 2
+            and len(key) > 1
+        ):
+            raise IndexingError("Too many indexers")
+
         if is_scalar(key) or (isinstance(labels, MultiIndex) and is_hashable(key)):
             # Otherwise get_loc will raise InvalidIndexError
 
@@ -1291,7 +1299,7 @@ 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_indexing.py

@@ -24,6 +24,7 @@
 )
 import pandas._testing as tm
 from pandas.core.api import Float64Index
+from pandas.core.indexing import IndexingError
 from pandas.tests.indexing.common import _mklbl
 from pandas.tests.indexing.test_floats import gen_obj
 
@@ -981,3 +982,31 @@ def test_extension_array_cross_section_converts():
 
     result = df.iloc[0]
     tm.assert_series_equal(result, expected)
+
+
+@pytest.mark.parametrize(
+    "ser, keys",
+    [(Series([10]), (0, 0)), (Series([1, 2, 3], index=list("abc")), (0, 1))],
+)
+def test_ser_tup_indexer_exceeds_dimensions(ser, keys, indexer_li):
+    # GH#13831
+    exp_err, exp_msg = IndexingError, "Too many indexers"
+    with pytest.raises(exp_err, match=exp_msg):
+        indexer_li(ser)[keys]
+
+    if indexer_li == tm.iloc:
+        # For iloc.__setitem__ we let numpy handle the error reporting.
+        exp_err, exp_msg = IndexError, "too many indices for array"
+
+    with pytest.raises(exp_err, match=exp_msg):
+        indexer_li(ser)[keys] = 0
+
+
+def test_ser_list_indexer_exceeds_dimensions(indexer_li):
+    # GH#13831
+    # Make sure an exception is raised when a tuple exceeds the dimension of the series,
+    # but not list when a list is used.
+    ser = Series([10])
+    res = indexer_li(ser)[[0, 0]]
+    exp = Series([10, 10], index=Index([0, 0]))
+    tm.assert_series_equal(res, exp)

pandas/tests/indexing/test_loc.py

@@ -2704,6 +2704,18 @@ def test_loc_with_period_index_indexer():
     tm.assert_frame_equal(df, df.loc[list(idx)])
 
 
+def test_loc_setitem_multiindex_timestamp():
+    # GH#13831
+    vals = np.random.randn(8, 6)
+    idx = date_range("1/1/2000", periods=8)
+    cols = ["A", "B", "C", "D", "E", "F"]
+    exp = DataFrame(vals, index=idx, columns=cols)
+    exp.loc[exp.index[1], ("A", "B")] = np.nan
+    vals[1][0:2] = np.nan
+    res = DataFrame(vals, index=idx, columns=cols)
+    tm.assert_frame_equal(res, exp)
+
+
 def test_loc_getitem_multiindex_tuple_level():
     # GH#27591
     lev1 = ["a", "b", "c"]
@@ -2959,11 +2971,11 @@ 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):