REF: No need to delegate to index check of whether an int is an int

Author: toobaz

doc/source/whatsnew/v0.23.4.txt

@@ -32,6 +32,7 @@ Bug Fixes
 
 - Bug where calling :func:`DataFrameGroupBy.agg` with a list of functions including ``ohlc`` as the non-initial element would raise a ``ValueError`` (:issue:`21716`)
 - Bug in ``roll_quantile`` caused a memory leak when calling ``.rolling(...).quantile(q)`` with ``q`` in (0,1) (:issue:`21965`)
+- Passing a non-int scalar to ``.iloc`` now raises a more appropriate error message (:issue:`21982`)
 -
 
 **Conversion**

pandas/core/indexing.py

@@ -2124,7 +2124,25 @@ def _getitem_scalar(self, key):
         return values
 
     def _validate_integer(self, key, axis):
-        # return a boolean if we have a valid integer indexer
+        """
+        Check that 'key' is a valid position in the desired axis.
+
+        Parameters
+        ----------
+        key : int
+            Requested position
+        axis : int
+            Desired axis
+
+        Returns
+        -------
+        None
+
+        Raises
+        ------
+        IndexError
+            If 'key' is not a valid position in axis 'axis'
+        """
 
         ax = self.obj._get_axis(axis)
         l = len(ax)
@@ -2215,8 +2233,6 @@ def _getitem_axis(self, key, axis=None):
 
         # a single integer
         else:
-            key = self._convert_scalar_indexer(key, axis)
-
             if not is_integer(key):
                 raise TypeError("Cannot index by location index with a "
                                 "non-integer key")

pandas/tests/indexing/test_floats.py

@@ -50,7 +50,7 @@ def test_scalar_error(self):
             def f():
                 s.iloc[3.0]
             tm.assert_raises_regex(TypeError,
-                                   'cannot do positional indexing',
+                                   'Cannot index by location index',
                                    f)
 
             def f():