BUG: reindexing a frame fails to pick nan value

pandas/src/klib/khash_python.h

@@ -5,7 +5,7 @@
 // kludge
 
 #define kh_float64_hash_func _Py_HashDouble
-#define kh_float64_hash_equal kh_int64_hash_equal
+#define kh_float64_hash_equal(a, b) ((a) == (b) || ((b) != (b) && (a) != (a)))
 
 #define KHASH_MAP_INIT_FLOAT64(name, khval_t)								\
 	KHASH_INIT(name, khfloat64_t, khval_t, 1, kh_float64_hash_func, kh_float64_hash_equal)

pandas/tests/test_base.py

@@ -674,6 +674,16 @@ def test_duplicated_drop_duplicates(self):
                 s.drop_duplicates(inplace=True)
                 tm.assert_series_equal(s, original)
 
+
+class TestFloat64HashTable(tm.TestCase):
+    def test_lookup_nan(self):
+        from pandas.hashtable import Float64HashTable
+        xs = np.array([2.718, 3.14, np.nan, -7, 5, 2, 3])
+        m = Float64HashTable()
+        m.map_locations(xs)
+        self.assert_numpy_array_equal(m.lookup(xs), np.arange(len(xs)))
+
+
 if __name__ == '__main__':
     import nose
 

pandas/tests/test_frame.py

@@ -9263,6 +9263,16 @@ def test_reindex(self):
         assert_frame_equal(result,self.frame)
         self.assertFalse(result is self.frame)
 
+    def test_reindex_nan(self):
+        df = pd.DataFrame([[1, 2], [3, 5], [7, 11], [9, 23]],
+                index=[2, np.nan, 1, 5], columns=['joe', 'jim'])
+
+        i, j = [np.nan, 5, 5, np.nan, 1, 2, np.nan], [1, 3, 3, 1, 2, 0, 1]
+        tm.assert_frame_equal(df.reindex(i), df.iloc[j])
+
+        df.index = df.index.astype('object')
+        tm.assert_frame_equal(df.reindex(i), df.iloc[j])
+
     def test_reindex_name_remains(self):
         s = Series(random.rand(10))
         df = DataFrame(s, index=np.arange(len(s)))

pandas/tests/test_index.py

@@ -740,7 +740,7 @@ def test_symmetric_diff(self):
         # expected = Index([0.0, np.nan, 2.0, 3.0, np.nan])
 
         nans = pd.isnull(result)
-        self.assertEqual(nans.sum(), 2)
+        self.assertEqual(nans.sum(), 1)
         self.assertEqual((~nans).sum(), 3)
         [self.assertIn(x, result) for x in [0.0, 2.0, 3.0]]
 

pandas/tests/test_series.py

@@ -5846,6 +5846,15 @@ def test_reindex(self):
         result = self.ts.reindex()
         self.assertFalse((result is self.ts))
 
+    def test_reindex_nan(self):
+        ts = Series([2, 3, 5, 7], index=[1, 4, nan, 8])
+
+        i, j = [nan, 1, nan, 8, 4, nan], [2, 0, 2, 3, 1, 2]
+        assert_series_equal(ts.reindex(i), ts.iloc[j])
+
+        ts.index = ts.index.astype('object')
+        assert_series_equal(ts.reindex(i), ts.iloc[j])
+
     def test_reindex_corner(self):
         # (don't forget to fix this) I think it's fixed
         reindexed_dep = self.empty.reindex(self.ts.index, method='pad')

setup.py

@@ -456,7 +456,8 @@ def pxd(name):
          'pxdfiles': [],
          'depends': lib_depends},
     hashtable={'pyxfile': 'hashtable',
-               'pxdfiles': ['hashtable']},
+               'pxdfiles': ['hashtable'],
+               'depends': ['pandas/src/klib/khash_python.h']},
     tslib={'pyxfile': 'tslib',
            'depends': tseries_depends,
            'sources': ['pandas/src/datetime/np_datetime.c',