From 4b868bfbbe5800af0fb037f35e688d307e336e5e Mon Sep 17 00:00:00 2001
From: tp <terji78@yaho.com>
Date: Fri, 15 Jun 2018 08:19:22 +0100
Subject: [PATCH] improve speed of nans in CategoricalIndex

---
 pandas/core/indexes/category.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/indexes/category.py b/pandas/core/indexes/category.py
index 7f2860a963423..0093d4940751e 100644
--- a/pandas/core/indexes/category.py
+++ b/pandas/core/indexes/category.py
@@ -326,7 +326,7 @@ def __contains__(self, key):
         hash(key)
 
         if isna(key):  # if key is a NaN, check if any NaN is in self.
-            return self.isna().any()
+            return self.hasnans
 
         # is key in self.categories? Then get its location.
         # If not (i.e. KeyError), it logically can't be in self either