BUG: fillna maximum recursion depth exceeded in cmp (GH18159).

Author: Krzysztof Chomski

doc/source/whatsnew/v0.22.0.txt

@@ -90,6 +90,7 @@ Bug Fixes
 - Bug in ``pd.read_msgpack()`` with a non existent file is passed in Python 2 (:issue:`15296`)
 - Bug in ``DataFrame.groupby`` where key as tuple in a ``MultiIndex`` were interpreted as a list of keys (:issue:`17979`)
 - Bug in :func:`pd.read_csv` where a ``MultiIndex`` with duplicate columns was not being mangled appropriately (:issue:`18062`)
+- BUG: fillna maximum recursion depth exceeded in cmp (:issue:`18159`)
 
 Conversion
 ^^^^^^^^^^

pandas/core/internals.py

@@ -1837,8 +1837,9 @@ def _can_hold_element(self, element):
         if tipo is not None:
             return (issubclass(tipo.type, (np.floating, np.integer)) and
                     not issubclass(tipo.type, (np.datetime64, np.timedelta64)))
-        return (isinstance(element, (float, int, np.floating, np.int_)) and
-                not isinstance(element, (bool, np.bool_, datetime, timedelta,
+        return (
+            isinstance(element, (float, int, np.floating, np.int_, np.long))
+            and not isinstance(element, (bool, np.bool_, datetime, timedelta,
                                          np.datetime64, np.timedelta64)))
 
     def to_native_types(self, slicer=None, na_rep='', float_format=None,