PERF: Don't create a CategoricalIndex._engine in __contains__ if categories are RangeIndex

Author: mroeschke

pandas/core/indexes/category.py

@@ -377,8 +377,11 @@ def __contains__(self, key: Any) -> bool:
         # if key is a NaN, check if any NaN is in self.
         if is_valid_na_for_dtype(key, self.categories.dtype):
             return self.hasnans
-
-        return contains(self, key, container=self._engine)
+        if self.categories._typ == "rangeindex":
+            container = self.categories
+        else:
+            container = self._engine
+        return contains(self, key, container=container)
 
     def reindex(
         self, target, method=None, level=None, limit: int | None = None, tolerance=None

pandas/tests/indexes/categorical/test_category.py

@@ -392,3 +392,10 @@ def test_remove_maintains_order(self):
                 ["a", "b", np.nan, "d", "d", "a"], categories=list("dba"), ordered=True
             ),
         )
+
+
+def test_contains_rangeindex_categories_no_engine():
+    ci = CategoricalIndex(range(3))
+    assert 2 in ci
+    assert 5 not in ci
+    assert "_engine" not in ci._cache