ENH: Improve error mesage verbosity in string accessor (#59900)

Author: KevsterAmp

pandas/core/strings/accessor.py

@@ -255,7 +255,9 @@ def _validate(data):
         inferred_dtype = lib.infer_dtype(values, skipna=True)
 
         if inferred_dtype not in allowed_types:
-            raise AttributeError("Can only use .str accessor with string values!")
+            raise AttributeError(
+                f"Can only use .str accessor with string values, not {inferred_dtype}"
+            )
         return inferred_dtype
 
     def __getitem__(self, key):

pandas/tests/series/accessors/test_str_accessor.py

@@ -15,7 +15,8 @@ def test_str_attribute(self):
 
         # str accessor only valid with string values
         ser = Series(range(5))
-        with pytest.raises(AttributeError, match="only use .str accessor"):
+        msg = "Can only use .str accessor with string values, not integer"
+        with pytest.raises(AttributeError, match=msg):
             ser.str.repeat(2)
 
     def test_str_accessor_updates_on_inplace(self):